In proportional circles, the size of each circle is proportional to the total value of the data it represents, e.g. the largest value is represented by the largest circle

Advantages of proportional circles

  • Proportional circles are suitable where it is necessary to compare absolute totals such as total crop production or export earnings in different periods.
  • They give a good visual impression of totality. This makes the comparison of totals easy as the size of each circle corresponds to the total amount it represents.
  • They can be combined with other methods on the same map to assist in data analysis especially when describing population distribution.

Disadvantages of proportional circles

  • This is a very tedious and rime-consuming method of representing data since the diameter and radii measurements have to be calculated.
  • It is not possible to determine the actual total values for each period from the circles since the totals are represented by the sizes of the circles.
  • Where the sets of data to be represented are many, the comparison of the circles becomes difficult.
  • Where the differences between the values being represented are too big, it becomes difficult to represent the extreme values as it results in very big and very small circles.

  • Where the differences in the values to be represented are very small, all the circles will be almost the same size, making comparison very difficult.




  • Easy to construct: Comparative bar graphs are relatively simple and straightforward to create. They involve drawing a series of bars to represent different data points, making it a convenient and efficient way to visually represent information.

  • Easy to read and interpret: Comparative bar graphs provide a clear visual representation of data, making them easy to read and understand. The bars allow for a quick comparison between different components or categories, enabling viewers to grasp the information at a glance.
  • Easy to compare similar components within different bars: The bar graph format makes it easy to compare similar components or categories within different bars. By aligning the bars side by side, you can visually compare their lengths and determine the relative values or quantities they represent.
  • Gives a good impression of totality: Comparative bar graphs provide a sense of the overall distribution or total quantity of the data being represented. The cumulative effect of all the bars gives a comprehensive view of the data set, allowing viewers to understand the complete picture.

  • Individual contribution made by each component is clearly seen: Each component or category represented by a bar in the graph can be easily identified and assessed. The length of each bar indicates the individual contribution or value of that component, enabling viewers to discern its importance or impact.
  • Differences in quantity of components are clearly seen: Comparative bar graphs excel at highlighting differences in quantity or magnitude between different components. The varying lengths of the bars make it easy to compare and identify variations in the data, helping to identify trends, disparities, or outliers.

Overall, comparative bar graphs offer a user-friendly and effective way to present and analyze data. They simplify complex information, allow for easy comparisons, and provide a visual representation that facilitates quick understanding and interpretation.


  • Doesn’t show trend of components over time: One limitation of comparative bar graphs is that they do not effectively depict the trend or change in components over time. Bar graphs are primarily used for comparing different categories or components at a specific point in time, and they do not provide a dynamic representation of how these components evolve or change over a period.
  • Not easy to compare components where bars are many: When a comparative bar graph contains a large number of components or categories, it can become visually crowded and challenging to compare individual bars accurately. The more categories there are, the smaller the bars become, making it difficult to discern differences in length or magnitude.
  • Not suitable for many components: Comparative bar graphs may not be suitable for data sets with a large number of components or categories. As mentioned earlier, a high number of bars can lead to visual clutter and hinder the clarity of the graph. In such cases, alternative visual representations like stacked bar graphs or other types of charts may be more appropriate.

  • Limited representation of data: Comparative bar graphs have a specific purpose of comparing different components or categories, but they may not be effective in conveying other aspects of the data. For example, if you want to showcase the distribution of data within each component or highlight relationships between variables, other types of graphs such as scatter plots or histograms might be more appropriate.
  • Lack of granularity: Bar graphs provide a broad overview and comparison of components, but they may not capture detailed or nuanced information. If you need to analyze data at a more granular level or examine subtle variations within each category, a different visualization method, such as a line graph or a stacked bar graph with smaller categories, might be more suitable.
  • Limited use for continuous data: Comparative bar graphs are generally used for representing categorical or discrete data, where each component represents a distinct category. They are less effective when dealing with continuous data, such as measurements on a scale or time series data. In such cases, line graphs or other continuous data visualization techniques are often preferred.
  • Dependency on accurate scale and labeling: To ensure the accuracy and interpretability of a comparative bar graph, it is crucial to have a well-defined and appropriately labeled scale. Inaccurate scaling or unclear labeling can distort the visual representation and lead to misinterpretation of the data. Careful attention should be given to the scale, axis labels, and units used in the graph.

It’s important to consider these limitations when deciding to use a comparative bar graph. While they have their advantages in certain contexts, other types of graphs or charts may be more suitable when dealing with time-based data, a large number of components, or when the emphasis is on tracking trends or patterns over time.




  • Simple to construct: Comparative line graphs are relatively straightforward to construct, requiring only a basic understanding of plotting points and connecting them with lines. The process involves plotting the data points for each variable along a common axis and then connecting them with lines to show the trend or movement over time or across categories.

  • Suitable for comparing trends or movements: Comparative line graphs are particularly useful when comparing trends or movements in data. They allow for a visual representation of how variables change over time or across different categories. By plotting the data points and connecting them with lines, it becomes easy to observe patterns, identify increases or decreases, and analyze the overall trend of each variable.
  • Comparison of items is easy: One of the advantages of comparative line graphs is that they use a common axis, usually representing time or categories, which makes it easy to compare different items or variables. Since all the lines are plotted on the same axis, it becomes effortless to assess how each variable is performing relative to the others. This allows for quick comparisons and insights into the relative magnitudes and changes in each variable.

  • Ability to read exact values: Comparative line graphs provide a visual representation of data points, allowing for the precise reading of values for each variable at specific points in time or categories. By examining the position of the data points on the graph and referring to the labeled axis, it is possible to determine the exact values for each variable. This feature makes it convenient for extracting specific data points or conducting detailed analysis.

Overall, comparative line graphs offer a simple and effective way to compare trends or movements in data. They facilitate easy comparisons, enable the visualization of patterns and trends, and provide a means to read exact values for each variable. These advantages make comparative line graphs a valuable tool for data analysis and communication in various fields.


  • Number of items which can be represented are limited
  • Crossing of lines may make interpretation and comparison difficult and confusing.
  • Total amount of variable cant be established at a glance.
  • Limited number of items: Comparative line graphs can become cluttered and difficult to read when representing a large number of items or variables. Each additional line adds complexity to the graph, and if there are too many lines, it becomes challenging to distinguish and compare them effectively. In such cases, alternative visualization methods, such as grouped bar charts or small multiples, may be more appropriate.

  • Difficulty in interpretation: When multiple lines cross or intersect in a comparative line graph, it can make interpretation and comparison challenging. The crossing of lines can create confusion, especially if the lines are close in value or exhibit similar trends. This can lead to ambiguity and make it difficult to draw clear conclusions or identify relationships between variables.
  • Limited ability to determine the total amount: Unlike some other graph types, such as stacked bar charts or area charts, comparative line graphs do not readily convey the total amount or sum of the variable being represented. Line graphs focus on tracking the changes and trends in individual variables over time or across categories, rather than providing an immediate sense of the total value.
  • Sensitivity to data fluctuations: Comparative line graphs are sensitive to the fluctuations and variations in data, particularly when representing data over time. Small fluctuations in the data can result in jagged lines, making it challenging to discern underlying patterns or trends. Smoothing techniques or moving averages can be employed to address this issue, but they may also obscure certain aspects of the data.

When using comparative line graphs, it is important to strike a balance between the number of items represented, the clarity of the lines, and the ease of interpretation. Careful selection of variables, appropriate scaling, and clear labeling can help mitigate some of the limitations and enhance the effectiveness of the graph in conveying the desired information.




  • Comprehensive representation: Combined line and bar graphs allow for the simultaneous representation of two different types of data or variables. This can provide a more comprehensive view of the information being presented. For example, you can use the bars to represent one variable and the line to represent another variable, allowing you to display multiple dimensions of data in a single graph.

  • Effective comparison: By combining both bars and lines, you can easily compare the values and trends of different variables or components. This can be particularly useful when there are relationships or dependencies between the variables being represented. The visual contrast between the bars and lines makes it easier to compare the magnitude of values and identify any patterns or trends.
  • Enhanced clarity: In certain cases, combining a bar graph and a line graph can enhance the clarity of the data presentation. The bars provide a clear visual representation of individual values or categories, while the line can help illustrate the overall trend or progression of the data. This combination can make it easier for viewers to understand the data and draw insights from it.
  • Efficient use of space: By combining both types of graphs, you can save space and reduce the number of graphs needed to represent the data. This can be particularly advantageous when presenting information in reports, presentations, or other contexts where space is limited. Using a combined line and bar graph allows you to present multiple sets of data in a concise and efficient manner.
  • Flexibility in data representation: Combined line and bar graphs offer flexibility in how data is represented. You can choose to emphasize one type of data over the other, adjust scales, or use different colors and formatting to highlight specific aspects of the data. This flexibility allows you to customize the graph to best suit the specific requirements of your data analysis and communication goals.

It shows relationship between two sets of data.


  • Difficult to choose a suitable scale: In combined line and bar graphs, the values of variables may differ significantly in magnitude. This can make it challenging to choose a suitable scale for the graph. If the scale is not selected carefully, it may result in one component dominating the graph, making it difficult to compare and interpret the data accurately.
  • Obscuring the relationship: When there is considerable variation in the data represented by the line graph, it can cause the bars to become less visible or even obscured. This can happen when the bars are relatively small compared to the fluctuations of the line. In such cases, the relationship between the two components may be difficult to perceive, leading to potential misinterpretation of the data.

  • Limited in showing relationships between multiple data sets: Combined line and bar graphs may not effectively show the relationship between the same sets of data from multiple places or categories. The combination of bars and lines may become cluttered and confusing when representing multiple data sets. It can be challenging to differentiate between the bars and lines representing different places or categories, making it difficult to compare the data effectively.
  • Potential for confusion: Combined line and bar graphs can sometimes be confusing for readers, especially if they are not familiar with the specific format. The presence of both bars and lines on the same graph can lead to visual clutter and may require additional effort from the reader to understand the information correctly. This can be a disadvantage, particularly when presenting data to a wide audience or when the graph needs to be quickly understood.
  • Complexity in interpretation: The combination of bars and lines in a single graph can introduce complexity in the interpretation of the data. Readers may need to mentally switch between focusing on the bars and the lines, making it more challenging to extract meaningful insights or comparisons from the graph. This complexity can hinder the quick and accurate interpretation of the data, especially if the relationships between the components are not clearly presented.

  • Limited to specific data relationships: Combined line and bar graphs are most useful when representing specific relationships between different components or variables. However, they may not be suitable for all types of data or data comparisons. For example, if the data does not exhibit a clear relationship or if there are multiple independent variables, a combined line and bar graph may not effectively communicate the information.




  • Easy construction: Simple bar graphs are straightforward to create, even for those with limited experience in data visualization. The graph consists of vertical or horizontal bars that represent the data values, making it a user-friendly option for presenting information.

  • Clear interpretation: The simplicity of a bar graph allows for easy interpretation. Viewers can quickly grasp the relative values and make comparisons between different categories or data points. The length or height of each bar represents the quantity or magnitude of the data, providing a clear visual impression.
  • Readability: Simple bar graphs are highly readable, as they present data in a visually intuitive manner. Viewers can easily identify and understand the values associated with each bar, enabling efficient data comprehension and analysis.
  • Visual impact: Bar graphs have a strong visual impact due to the distinct and recognizable shape of the bars. The clear and prominent representation of data quantities aids in conveying the significance of the information being presented. This can be particularly helpful in capturing the attention of the audience and emphasizing key points.
  • Comparison of data: Simple bar graphs excel in facilitating comparisons between different categories or data points. The lengths or heights of the bars provide a visual means of comparing quantities, making it easier to identify patterns, trends, or disparities in the data.
  • Versatility: Simple bar graphs can be applied to various types of data, including categorical or numerical data. They can be used to represent discrete categories or continuous variables, making them a versatile option for a wide range of data analysis and reporting needs.


  • Exaggeration of bars: If the vertical scale chosen for the bar graph is not appropriate, it can lead to the exaggeration or distortion of the bars. This can misrepresent the relative values of the data and potentially lead to inaccurate interpretations. Care should be taken to select a suitable scale that accurately reflects the magnitude of the data.
  • Lack of continuity: Simple bar graphs are not ideal for showing the continuity or variation of data over time. They are primarily used for comparing discrete categories or data points. If you need to visualize the changes in data values over time or demonstrate a continuous relationship, other graphing techniques such as line graphs or scatter plots may be more suitable.
  • Unsuitability for continuous values: Simple bar graphs are most effective when representing categorical or discrete data. They are less suitable for displaying data with a continuous range of values. Since the bars in a simple bar graph are separate and not connected, they do not accurately depict the continuous nature of the data.
  • Limited information on intermediate values: Simple bar graphs provide a visual representation of the distinct values or categories but do not provide specific information about intermediate values within each bar. It can be challenging to obtain precise numerical values from the graph, especially when trying to determine values between the marked data points.
  • Limited data comparison: While simple bar graphs are excellent for comparing values within a single category or data set, they may not be as effective for comparing data across multiple categories or data sets. When dealing with complex comparisons or a large number of data points, alternative graphing techniques like stacked bar graphs or grouped bar graphs may be more appropriate.



A line graph is a graphical representation of data that uses points connected by lines to show the relationship between two variables. It is a type of chart that is used to display data that changes over time or is plotted along a number line.


  • Ease of construction: Simple line graphs are relatively easy to construct compared to more complex types of graphs. They require plotting data points on a graph paper or using graphing software, connecting the points with straight lines, and labeling the axes. The simplicity of the construction process makes line graphs accessible to a wide range of users.
  • Ease of interpretation: Simple line graphs are intuitive and easy to interpret. The line connecting the data points visually represents the trend or movement of the data over time or another independent variable. It allows viewers to quickly understand whether the values are increasing, decreasing, or remaining relatively stable.
  • Easy reading of exact values: Simple line graphs provide a visual representation of data points along a continuous line. This allows viewers to estimate or read the exact values of the data at specific points in time or along the x-axis. The graph can be used as a reference to determine the precise values without the need for detailed calculations or interpolations.

  • Trend visualization: Simple line graphs excel at showing trends or patterns in data over time or across a continuous independent variable. The slope and direction of the line provide insights into the direction and magnitude of changes, helping users identify long-term trends, seasonal patterns, or fluctuations in the data.


  • Lack of clarity on quantity: A simple line graph may not provide a clear impression of the quantity of data, especially when the lines are relatively close together or when the data points are clustered. This can make it difficult to compare and interpret the data accurately.
  • Potential for false impressions: If there are gaps or missing data points in the dataset, a simple line graph may give a false impression of the quantity, especially when there is no production or data available for certain periods. This can lead to misleading interpretations if not considered in the analysis.

  • Exaggerated fluctuations: Depending on the chosen vertical scale, a simple line graph may exaggerate or minimize the fluctuations in values. If the scale is not appropriately chosen, even small changes in the data may appear significant, leading to a distorted representation of the trends or patterns.
  • Difficulty in obtaining precise values: Unlike other types of graphs, such as bar graphs or scatter plots, a simple line graph may not allow for precise determination of values by interpolation. Interpolation involves estimating values between data points, and it can be challenging to obtain exact values from a simple line graph due to its continuous nature.

Considering these disadvantages, it’s essential to carefully select the appropriate graph type based on the nature of the data and the specific insights or comparisons you aim to convey. Different graph types may better suit different scenarios and data representations, so it’s important to choose the most suitable graph for effective communication and interpretation of the data.



  • Draw boundaries of the statistical units if they are not already provided on the base map.
  • Calculate the average densities for each statistical unit by dividing the quantities in each unit by the unit area.

  • Determine a suitable scale of densities to be used in shading the map.
  • Indicate lightly in pencil on the map the grade of shading or colouring to be used for each area.
  • Shade or colour the map, erasing figures and all other unnecessary information but leaving boundary lines.
  • Give a title and key to the map.
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Note the following;

  1. The shading should show a progressive increase in density. Avoid a blank since it gives a wrong impression.
  2. The range of values may be divided in groups by either arithmetic progression when the range is not great.
  3. Variation in density can also be shown by proportional shading.
  4. Do not show variation in density by merely drawing lines at different angles.
  5. A more pleasing appearance of continuity and transition can be achieved if shading lines are carried a cross as far as possible from one statistical unit to the next.
  6. It is advisable to use a key with individual boxes. The key should be complete with all the grades of shading.


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