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How to fix an invalid data type

Asked by Annika Banuelos on 12 Sep 2019
Latest activity Commented on by Walter Roberson
on 12 Sep 2019
This is my script,
%This script calculates some statistics for the wine data
load('winedata');
A=winedata; %matrix
max=max(A);
min=min(A);
sigma=std(A);
mean=mean(A);
% End of script
Error using max
Invalid data type. First argument must be numeric or logical.
Error in Wine_Data (line 7)
max=max(A);
How would I fix this?

  1 Comment

What shows up for class(A) ?

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2 Answers

Answer by David Hill
on 12 Sep 2019

Max=max(A)%do not name variable max or min

  1 Comment

This is a good idea, but unfortunately in itself it will not solve the problem.

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Answer by J Chen
on 12 Sep 2019

The winedata may contain some strange characters. Carefully exame elements of windata. Command class(A) should return 'double'.

  1 Comment

When you do
mean=mean(A);
the first time, then there is no variable named mean so MATLAB looks along the search path and finds a function named mean and uses the function. Then you are assigning the result to the variable mean
The second time through, you have a variable named mean so mean(A) is interpreted as trying to index into the variable.
With the script you posted, if you only execute the script once, then you do not have a problem in that code immediately, but you do leave variables mean and min and max in the base workspace, where they will cause problems if you try to execute the script again, or try do use any of those three at the command line or in another script.
You should learn to use functions, and you should avoid using variables that are the same name as any of the common library routines.

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