# How to calculate mid value of RGB image in matlab?

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Aarach Sap on 29 Sep 2016
Commented: Stephen23 on 29 Sep 2016
I did
c= mid(RGB(:));
And I got an error saying "Undefined function 'mid' for input arguments of type 'double'"
Stephen23 on 29 Sep 2016
You possibly meant to call the median function, where the median is the standard mathematical term for the "mid value" of a set of values:
Or perhaps the mean, where the mean is the standard mathematical term for the "average" of a set of values:

Walter Roberson on 29 Sep 2016
If you are referring back to that rgb2hsv and hsv2rgb C++ code you posted the link to, https://bitbucket.org/chernov/colormath/src/012a5ae28033dc8e91ec66ec349c95d81caddb71/colormath/hsv.cpp?at=default&fileviewer=file-view-default, then beware.
In the first of the routines there, rgb2hsv, mid is used as a variable that holds a copy of the value of one of the three color components. If you were to vectorize the code, then mid should be an array of values, not a function.
In the second of the routines there, hsv2rgb, mid is used as a pointer to one of the output values r, g, b, and after all the rest of the calculations, the value at that pointer is modified. If you were to vectorize the code, then you would need to make mid an array of indicators of which of the three values is to be modified for that location. The easiest way to do that would be to put your rgb together into a 3D array and then have mid be indices into the third dimension.