Graphics |
Pie Charts
Pie charts display the percentage that each element in a vector or matrix contributes to the sum of all elements. pie
and pie3
create 2-D and 3-D pie charts.
Example -- Pie Chart
Here is an example using the pie
function to visualize the contribution that three products make to total sales. Given a matrix X
where each column of X
contains yearly sales figures for a specific product over a five-year period,
sum each row in X
to calculate total sales for each product over the five-year period.
You can offset the slice of the pie that makes the greatest contribution using the explode
input argument. This argument is a vector of zero and nonzero values. Nonzero values offset the respective slice from the chart.
First, create a vector containing zeros.
Then find the slice that contributes the most and set the corresponding explode
element to 1
.
The explode
vector contains the elements [0 0 1]
. To create the exploded pie chart, use the statement
Labeling the Graph
The pie chart's labels are text graphics objects. To modify the text strings and their positions, first get the objects' strings and extents. Braces around a property name ensure that get
outputs a cell array, which is important when working with multiple objects.
textObjs = findobj(h,'Type','text'); oldStr = get(textObjs,{'String'}); val = get(textObjs,{'Extent'}); oldExt = cat(1,val{:});
Create the new strings, then set the text objects' String
properties to the new strings.
Names = {'Product X: ';'Product Y: ';'Product Z: '};
newStr = strcat(Names,oldStr);
set(textObjs,{'String'},newStr)
Find the difference between the widths of the new and old text strings and change the values of the Position
properties.
val1 = get(textObjs, {'Extent'});
newExt = cat(1, val1{:});
offset = sign(oldExt(:,1)).*(newExt(:,3)-oldExt(:,3))/2;
pos = get(textObjs, {'Position'});
textPos = cat(1, pos{:});
textPos(:,1) = textPos(:,1)+offset;
set(textObjs,{'Position'},num2cell(textPos,[3,2]))
Comparing Data Sets with Area Graphs | Removing a Piece from a Pie Chart |
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