Calculating mean and variance , iris dataset

Question

mary keshtkar 2022-11-6

1
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1844773-calculating-mean-and-variance-iris-dataset

评论： NALLARASU KRISH 2024-2-23

I would like to calculate mean an variance for iris dataset(for the first species) . How can i clean my code! Make it two for loop (one loop for mean , one loop for variance?

 load fisheriris
 a=meas(1:50,1:end);
 a1=a(1:50,1);
 a2=a(1:50,2);
 a3=a(1:50,3);
 a4=a(1:50,4);
 s1=0;
 for i=1:50;
     s1=s1+a1(i);
 end
 mean1=s1/50
 s2=0;
 for j=1:50;
     s2=s2+a2(j);
 end
 mean2=s2/50
 s3=0;
 for k=1:50;
     s3=s3+a3(k);
 end
 mean3=s3/50
 s4=0;
 for l=1:50;
     s4=s4+a4(l);
 end
 mean4=s4/50
 means=[mean1,mean2,mean3,mean4]
 v1=0;
 for p=1:50;
     v1=v1+(a1(p)-mean1)^2;
 end
 var1=v1/49
 v2=0;
 for o=1:50;
     v2=v2+(a2(o)-mean2)^2;
 end
 var2=v2/49
v3=0;
for u=1:50;
   v3=v3+(a3(u)-mean3)^2;
end
var3=v3/49
v4=0;
for t=1:50;
   v4=v4+(a4(t)-mean4)^2;
end
var4=v4/49
 totalvar=[var1 var2 var3 var4]

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Answer 1

Kevin Holly 2022-11-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1844773-calculating-mean-and-variance-iris-dataset#answer_1092548

在 MATLAB Online 中打开

Is there a reason why you aren't using the mean and var function?

load fisheriris
a=meas(1:50,1:end);
means = mean(a)
means = 1×4
    5.0060    3.4280    1.4620    0.2460
totalvar = var(a)
totalvar = 1×4
    0.1242    0.1437    0.0302    0.0111

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Kevin Holly 2022-11-6

在 MATLAB Online 中打开

Also, if you are allowed to use sum function:

load fisheriris
a=meas(1:50,1:end);
means = sum(a(1:50,:))/50
means = 1×4
    5.0060    3.4280    1.4620    0.2460
totalvar = sum((a(1:50,:)-means).^2)/49
totalvar = 1×4
    0.1242    0.1437    0.0302    0.0111