how to write a correlation coefficient code with only the use of SUM function.

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alexander fastiggi
alexander fastiggi 2019-11-1
评论： Walter Roberson 2019-11-1
how to write a correlation coefficient code with only the use of SUM function.
YES, you can not just use
corrcoef(x,y)
mean(x) mean(y)
std(x) std(y)
to write this code.
literally writing a function to find correlation coefficient with SUM as the only intrinsic function

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回答（1 个）

Walter Roberson
Walter Roberson 2019-11-1
That is not possible. The Pearson Correlation Coefficient cannot be calculated without multiplications or divisions.
https://en.wikipedia.org/wiki/Pearson_correlation_coefficient#For_a_sample
Notice the use of . That is defined as which is something that cannot be calculated without at least one division.
  2 个评论
Walter Roberson
Walter Roberson 2019-11-1
Yes you did!! I quote,
with only the use of SUM function
In MATLAB, multiplication and division are functions. The .* operator is formally known as times and the ./ operator is formally known as rdivide . .* and ./ are "syntax sugar" .
A .* B
is exactly the same as times(A, B) -- a function call.
In MATLAB, neverly everything is a function. Subscripting is a function. Assignment is the function whose formal name is subsasgn() .
These are the only things in MATLAB that are not functions:
>> iskeyword
ans =
20×1 cell array
{'break' }
{'case' }
{'catch' }
{'classdef' }
{'continue' }
{'else' }
{'elseif' }
{'end' }
{'for' }
{'function' }
{'global' }
{'if' }
{'otherwise' }
{'parfor' }
{'persistent'}
{'return' }
{'spmd' }
{'switch' }
{'try' }
{'while' }

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