## Getting error when asking from max and min for negative values.

Yasmin Samy

### Yasmin Samy (view profile)

さんによって質問されました 2017 年 12 月 27 日

### Yasmin Samy (view profile)

さんによって コメントされました 2017 年 12 月 27 日
Image Analyst

### Image Analyst (view profile)

さんの 回答が採用されました
I have two vector of negative numbers (log values). The first is fine as it has a postive max value and a negative min. But i get an error for the second vector (which has its max and min as negative numbers) when i ask for max or min. What is another option to get these two values??
error: Subscript indices must either be real positive integers or logicals.

Rik

### Rik (view profile)

on 27 Dec 2017
What code are you using? Are you using the min and max functions? The error sounds like you aren't.
Yasmin Samy

### Yasmin Samy (view profile)

on 27 Dec 2017
the vector is A, the code lines are:
max=max(A);
min=min(A);

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## 2 件の回答

### Image Analyst (view profile)

on 27 Dec 2017

Sounds like you may be trying to index into the array using the min or max value instead of the index:
mn = min(data);
minValue = data(mn);
Don't do that. Use both values if you want to get the index. A better way:
[minValue, indexOfMin] = min(data);
[maxValue, indexOfMax] = max(data);
Or you may have used min for the variable
min = min(data); % Horrible idea
in which case when you came along and tried to do it again, it would have used your min array (a vector is data was a 2-D array) as indexes into your newly created min array. min() is no longer the min function if you replaced it with a variable of the same name. So if the min was now an array of column mins because you stored the mins in an array called min, then doing min(data) will throw that error if any elements of data have negative, zero, or floating points (fractional) values.

Yasmin Samy

### Yasmin Samy (view profile)

on 27 Dec 2017
Ah!! ok thanks you guys!
You are right. It works now. :)

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### Walter Roberson (view profile)

on 27 Dec 2017

Do not name a variable min or max. Also do not name a variable sum . Using any of these variable names is quite likely to run into problems when you later try to use the same name as if it were the MATLAB function.

Yasmin Samy

### Yasmin Samy (view profile)

on 27 Dec 2017
Yes you are right. Luckily, its not the cause of my problem. As the vector im having an issue with i used omax and omin as the name of the values for the maximum and min. So it's like omax=max(oA);
Yasmin Samy

### Yasmin Samy (view profile)

on 27 Dec 2017
Thanks...it seems using it in the first place messed things

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