Create an error function

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udi ibgui
udi ibgui 2019-11-18
编辑： munue 2019-11-18
Hi,
I have 2 matrices of images, with all values 0 and 1. I would like to compare the two, where i would like to get the number of true positives (where both pixels -at the same postion- are equal to 1), true negatives (both pixels equal to 0), false positives ( where image A is equal to 1 but image B is equl to 0) and false negatives (where image A is equal to 0 but image B is equal to 1).
If I try to extract where A==1 and B==1 etc. and compare it, I get an error because the matrices dont agree.
If I just compare A to B I only get where the match/not match but it doesnt tell me if its a true positive etc.
thank you
  2 个评论
KSSV
KSSV 2019-11-18
YOu can use :
idx = A == B ;
Apply your formula on matrix idx.
udi ibgui
udi ibgui 2019-11-18
编辑：udi ibgui 2019-11-18
What do you mean by apply formula?
The above code shows 1 whenever they match and 0 whenever they dont. It doesnt tell me if the match was becasue they were both 1 or both 0

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munue
munue 2019-11-18
编辑：munue 2019-11-18
You can try the following:
A=[1 0; 0 1]
B=[1 0 ; 1 0]
TruePositive_idx = find (A==B & A==1)
TrueNegative_idx = find (A==B & A==0)
FalseNegative_idx = find (A~=B & A==1)
FalsePositive_idx = find (A~=B & A==0)

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