Standard deviation, Mean values for each class

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Ivan Mich
Ivan Mich 2020-3-24
评论： Adam Danz 2020-3-25
Hello, I have a problem with a code.
First of all I have a .csv file with 2 columns, as I show you in the Image. in the first column the data are split by 0.5 (1,1.5,2).
I would like to find mean values and standard deviation for each of one class, I mean one value of standard deviation and mean value for the data with 1 in , one value of standard deviation for the 1.5 and one value of standard deviation for the 2.
I mean I wanna use the errorbar command.
I think I should use a loop who reads 1st column one by one but I can not make it.
Could anyone help me?

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Adam Danz
Adam Danz 2020-3-24
编辑：Adam Danz 2020-3-24
Use grpstats() if you have the Stats & Machine Learning Toolbox.
data = [ 1 1 1.5 1.5 2 2; 10 9 7 6 3.5 8]',;
[dataMean, dataStd] = grpstats(data(:,2), data(:,1), {'mean', 'std'})
If your data are in table format,
Tstats = grpstats(T, 'data1', {'mean','std'});
% ^^^^^ VariableName for column 1
If you don't have Stats & Machine Learning Toolbox,
stats = splitapply(@(x)[mean(x), std(x)], data(:,2), findgroups(data(:,1)));
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Ivan Mich
Ivan Mich 2020-3-25
编辑：Adam Danz 2020-3-25
well, I send you the full code in order to see it and tell me where I am wrong:
clc
clear
filename1= 'e.xlsx'
[d1,tex]= xlsread(filename1);
x=d1(:,1);
y=d1(:,2);
stats = splitapply(@(y)[mean(y), std(y)], y, findgroups(x));
meanvalues=stats(:,1)
stdvalues=stats(:,2)
err=errorbar(meanvalues,stdvalues)
% lower error line
hold on
plot(x,y,'bo')
hold on
plot(x, y-err)
hold on
% upper error line
plot(x, y+err)
Command window send me the message :
Undefined operator '-' for input arguments of type 'matlab.graphics.chart.primitive.ErrorBar'.
Error in eo (line 24)
Adam Danz
Adam Danz 2020-3-25
plot(x, y-err)
plot(x, y+err)
1) You should be using the meanvalues insetad of x.
2) err, in your code, is the handle to the error bars. You should be using the stdvals.

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