Using min() on vectors with double

Question

Kylie Hansen 2017-7-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/347643-using-min-on-vectors-with-double

回答： PARAS PATIL 2019-11-6

I have several variables of the double type, each around 450x1 in size. I would like to find the minimum value of each of them, but when I use min(vector), MATLAB returns "Subscript indices must either be real positive integers or logicals." Does this mean that min() cannot work with decimals? If so, is there another function I can use that will? An example of my code is below. As you can see, I have set up a matrix that has two columns, one with a single integer and another with the minimum value of the vector.

min_set = [974,min(blg0974);975,min(blg0975);976,min(blg0976)];

Update: All my vectors have positive values with decimal places up to the ten thousandth's place.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Stephen 2017-7-6

min should work with double type. The error message you reported and the line supplied leads me to believe there is a variable in your workspace named "min". Is that the case?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Geoff Hayes 2017-7-6

4
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/347643-using-min-on-vectors-with-double#answer_273131

编辑：Geoff Hayes 2017-7-6

在 MATLAB Online 中打开

Kylie - try typing

which min

to see if min refers to the function to find the minimum value of an array or if min refers to a local variable. If you are seeing the above error message when you call min(vector), then this suggests that you are trying to access elements in an array named min with non-integer indices (which would be the floats or doubles in your vectors/arrays). If this is the case, then you can easily fix this problem by renaming your local variable to something else which will not correspond to a built-in MATLAB function.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Kylie Hansen 2017-7-6

I wasn't familiar with the which command. I've learned something new today! Thank you so much. The issue is solved, and I can go back to work headache-free.

请先登录，再进行评论。

Answer 2

dpb 2017-7-6

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/347643-using-min-on-vectors-with-double#answer_273132

在 MATLAB Online 中打开

"when I use min(vector), MATLAB returns "Subscript indices must either be real positive integers or logicals."

This means you've inadvertently aliased the MIN() function and Matlab now sees min(blg0974) as an array reference.

To confirm this diagnosis, execute

which min

and it will return "min is a variable". To fix this problem, execute

clear min

and remember to not do that again! :)

Illustration of the above to reproduce your symptom:

>> min=min(rand(3))  % call MIN(), forget and name output as min, too...
min =
  0.5936    0.2439    0.3485
>> min(min)          % try to get overall minimum of the column minima above
Subscript indices must either be real positive integers or logicals. 
>>

Oops! Look familiar? :)

>> which min           % Whassup???
min is a variable.       % Aha!  Of course and arrays can't have fractional subscripts
>> clear min             % fix the mistake...
>> which min             % and back to normal...
built-in (C:\ML_R2014b\toolbox\matlab\datafun\@logical\min)  % logical method
>>

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Kylie Hansen 2017-7-6

Thank you for such a detailed response. I am familiar with the mistake of naming variables after functions, but I had too many variables in my workspace that I hadn't noticed that I had set it as such. I will definitely keep your advice in mind! Thanks again.

请先登录，再进行评论。