How to fix an invalid data type

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?

[Walter Roberson]

What shows up for class(A) ?

[Rik]

Why did you flag your own question as unclear? (just to make sure you don't try anything funny: here's an archive)

Answer 1

[David Hill]

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

[Walter Roberson]

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

Answer 2

[J Chen]

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

[Walter Roberson]

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.