Problem with logical indexing

3 次查看(过去 30 天)
I'm trying to write a function that will take a row vector of temperatures as input and will give the number of temperatures below 32° as output. I have tried this:
function numfreeze = freeezing(temperatures)
numfreeze = numel(freezing(freezing<32))
end
...but I get the error message "Out of memory. The likely cause is an infinite recursion within the program."
Can someone help me and tell me what this means? When I just use
numfreeze = numel(freezing(freezing<32))
in the command window after setting a vector for "temperatures", it works fine.

采纳的回答

Guillaume
Guillaume 2019-4-24
编辑:Guillaume 2019-4-24
freezing is the name of the function. So when you write freezing inside the function, you're telling it to call itself. Of course, once it's called itself, it reexecute that freezing call ad finitum. Hence the infinite recursion.
You probably meant to use the input variable temperatures inside that function
function numfreeze = freeezing(temperatures)
numfreeze = numel(temperatures(temperatures<32))
end
While the above will work, it's not the most efficient. You're deleting all the elements above 32 to then find out how many remain. It be simpler to just count how many true values are in your logical array and not bother with the deletion, so:
function numfreeze = freeezing(temperatures)
numfreeze = nnz(temperatures<32); %you can also use sum instead of nnz
end
  1 个评论
RP
RP 2019-4-24
Thank you so much, this works and I didn't know nnz before!

请先登录,再进行评论。

更多回答(2 个)

Alex Mcaulley
Alex Mcaulley 2019-4-24
I think you have a typo, calling infinite times the function freezing, then:
function numfreeze = freeezing(temperatures)
numfreeze = numel(temperatures(temperatures<32))
end

Ajith Thomas
Ajith Thomas 2019-7-19
function numfreeze=freezing(w)
lowerthan_32=w(w<32);
no_logical_values=lowerthan_32(lowerthan_32>=0);
numfreeze=length(no_logical_values);
end
  1 个评论
Ajith Thomas
Ajith Thomas 2019-7-19
function numfreeze=freezing(w)
lowerthan_32=w(w<32);
numfreeze=numel(lowerthan_32);
end

请先登录,再进行评论。

类别

Help CenterFile Exchange 中查找有关 Matrix Indexing 的更多信息

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by