variance explained & pca

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Alberto Acri 2021-1-10

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https://ww2.mathworks.cn/matlabcentral/answers/713038-variance-explained-pca

评论： Ive J 2021-1-15

Hi! I want to report in a graph the variances explained as a function of PCs as shown in the graph. I have used the function "pareto(ExplVar)" but only the first 10 are represented and not all (there are 20 PCs in total). How can I represent them all?

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Anmol Dhiman 2021-1-13

Hi Alberto ,

Could you share your code for better resolution of the issue

Alberto Acri 2021-1-13

在 MATLAB Online 中打开

The code is long. I have considered

p = pareto(ExplVar)

where ExplVar is an array 10000x1.

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Ive J 2021-1-13

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编辑：Ive J 2021-1-13

在 MATLAB Online 中打开

pareto only shows the first 10 bars at maximum. You can do it easily with help of cumsum:

[~, ~, ~, ~, explained] = pca(rand(100,20));
hold on
bar(explained)
plot(1:numel(explained), cumsum(explained), 'o-', 'MarkerFaceColor', 'r')
yyaxis right
h = gca;
h.YAxis(2).Limits = [0 100];
h.YAxis(2).Color = h.YAxis(1).Color;
h.YAxis(2).TickLabel = strcat(h.YAxis(2).TickLabel, '%');

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Alberto Acri 2021-1-15

在 MATLAB Online 中打开

In this

[~, ~, ~, ~, explained] = pca(rand(100,20))

Should I introduce the PCs I found?

Ive J 2021-1-15

If you are calculating PCs with MATLAB pca built-in function, it can also return explained variances of PCs (explained in above example). If you want to show these explained variances (cumulatively), use explained; otherwise use PC scores if you prefer. It depends on your purposes of course (even you can use anything else to plot), but regardless, you can use my above example to reproduce similar graphs as pareto does, but without it's limitations (i.e. max 10 bars).

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