# error in std for 3d matrix

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Anastasia 2016 年 12 月 12 日
コメント済み: Guillaume 2016 年 12 月 13 日
Hey guys!
I am trying to find the std of a 3D matrix, where size(X) is 207 x 201 x 34. Since I must reshape to find std, I am using this formula: std(reshape(X,1,207*201*34)).
And I obtain this error: Error in std (line 31) y = sqrt(var(varargin{:}));
When I look at the syntax, I thought of using std(reshape(X,1,207*201*34), 0, 3), where 3 is for 3D, however I still obtain the same error.
What I am missing?
Thank you very much in advance!
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Anastasia 2016 年 12 月 13 日

Hello, this is the full text of the error message:
Error using var (line 58) First argument must be single or double.
Error in std (line 31) y = sqrt(var(varargin{:}));
Error in Code3D (line 27) th=mean(mean(mean(X))) + std(reshape(X,1,207*201*34));
Is the problem that X is nor single nor double, but 207*201*34? How can I fix that?
Thank you!

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### 回答 (2 件)

Isabella Osetinsky-Tzidaki 2016 年 12 月 12 日
try std(x(:))
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Anastasia 2016 年 12 月 13 日
Hello! Thank you for your answer but I obtain the same error...

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Guillaume 2016 年 12 月 13 日
Error: First argument must be single or double
Well, clearly, your first argument (a transform of X) is not single or double. So what is:
class(X)
If it's an integer type:
Xdouble = double(X);
th = mean(Xdouble(:)) + std(Xdouble(:));
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Guillaume 2016 年 12 月 13 日
Without context it's impossible to say if it's correct or not. Certainly, if you want the standard deviation of your integers, you have to convert them to double. If an integer result is then required, you can convert the output back to uint16 (with the loss of precision that it entails).

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