MATLAB: Problem with the mean function

mean

hiiii, I want to calculate the mean value for the frames which are extracted from a video .I use mean=mean(X) but there is some error has been occured.so can you please suggest me the answer for calculating the mean value of extracted frames.

Best Answer

When you did

mean = mean(X)

that will work the first time, calculating the mean and storing the result in the variable named "mean".

But the second time you ask to execute it, mean(X) does not refer to the function mean, it refers to the variable "mean" that you assigned the calculation to.

Solution: never use a variable name which is the same as the name of a function you might want to call, because as soon as you do the assignment, the name stops referring to the function and starts referring to the variable.

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MATLAB: How to make the code simpler

Try something like:

for i=1:num_elems %assuming you know the number of elements and have set it before hand
  eval(['TB(i) = mean(T' num2str(i) 'B);'])
end

What this does is that it evaluates the string as matlab code. Using eval is not recommended in general, but might make life easier for you here. (See Using Eval)

MATLAB: Calculate 2 standard deviations

Hi Chris, for a matrix of data

x = randn(10,4);
mean(x)+2*std(x)
mean(x)-2*std(x)

gives the sample means of the columns plus/minus 2 times the standard deviation. The question is whether you really want the sample standard deviation here, or the standard error of the mean.

Wayne

Best Answer

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MATLAB: How to make the code simpler

MATLAB: Calculate 2 standard deviations

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