Comparative Analysis


The image below shows the comparison between a histogram and the pie chart:

Histogram and pie charts
Source:chartio.com

Pie Chart


Pie Charts are A pie chart shows how some total amount is divided among distinct categories as a circle (the namesake pie) divided into radial slices. Each category is associated with a single slice whose size corresponds with the category’s proportion of the total. The data below shows the carburetors using pie chart :



Bar Graph


A bar chart depicts numeric values against distinct categories in a two-axis plot. On one axis, the category levels are listed. For each category, one bar is plotted, and its length along the other axis corresponds with the numeric value associated with the category. The below bar chart shows the comparison between mpg of the car and the carburetors in the car.



Why histograms display the data more efficiently?


While the example above demonstrates how the same data can be plotted in multiple ways, do not make the mistake of thinking that they are always interchangeable. With a bar chart, there is freedom on the numeric value axis to choose whatever values you’d like. For numeric values that indicate metric totals or data point counts, the sums across groups will tend to be equal to the sum across the data as a whole. In cases like this, a pie chart is just as valid as a bar chart as a visualization choice.

However, if the numeric values indicate some other statistic where the sum across groups does not equal the statistic ignoring groups, that’s when we run into problems. Examples include taking the average of a metric (e.g. average spend by user type) or if we look at proportions that are independent (e.g. proportion of survey respondents who use each of the polled apps). A bar chart is fine for this case, but a pie chart falls short. Since the circular shape implies that slices are parts of a whole, it is too easy for a reader to mistake a sum of slices as a representative of some sort of total.