# グラフでの座標の最大​値、最小値を出すには​どうすればいいですか​？

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R on 15 Nov 2022
Commented: R on 15 Nov 2022
biplotでグラフを出しました。
このグラフにおける成分1, 成分2の最大値, 最小値を出す方法をご教授ください。
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### Accepted Answer

Hernia Baby on 15 Nov 2022
Edited: Hernia Baby on 15 Nov 2022
まずデータを作ります
clear; clc; close all
u1=5*randn(1,10000);
u2=randn(1,10000);
x1=1/2^0.5*u1+1/2^0.5*u2;
x2=1/2^0.5*u1-1/2^0.5*u2;
X=[x1 ; x2]';
pcaを行います
[coef, score] = pca(X);
biplot(coef,'Scores',score);
---------

ここで注意ですがベクトルの方向によって最大と最小が逆になります
このグラフでと書いていますので正規化して算出しています
Cp1_max_min = [max(score(:,1)),min(score(:,1))]./max(abs(score),[],'all')
Cp1_max_min = 1×2
1.0000 -0.8342
Cp2_max_min = [max(score(:,2)),min(score(:,2))]./max(abs(score),[],'all')
Cp2_max_min = 1×2
0.1822 -0.1752

figure
hold on
biplot(coef,'Scores',score);
[~,idx] = max(score(:,1));
cp1max = score(idx,:);
[~,idx] = max(score(:,2));
cp2max = score(idx,:);
cpmax = [cp1max;cp2max];
scatter(cpmax(:,1)./max(abs(score),[],'all'),cpmax(:,2)./max(abs(score),[],'all'),'k')
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R on 15 Nov 2022
ありがとうございます。

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