Matlab corresponding values between matrices?

So i have these two matrices:

A =

745 780 800 860 810

780 780 760 695 815

744 825 720 690 750

715 860 700 670 620

B =

30 18 40 58 26

70 19 72 29 47

14 48 40 14 48

13 72 59 66 72

I want the user to enter a number N so the program will show how many of A's values are lower than the number the user typed. I did this with this command:

N=input('Type a number :')
C= nnz(A<N)

But now i want the program to show me the values of B that correspond to the A's values that are lower than the N number

(Sorry about my bad english, any ideas?)

Answer 1

[Image Analyst]

Try this:

A = [...
   745   780   800   860   810
   780   780   760   695   815
   744   825   720   690   750
   715   860   700   670   620]
B = [...
   30   18   40   58   26
   70   19   72   29   47
   14   48   40   14   48
   13   72   59   66   72]

% N = input('Type a number : ')
N = 745;
% Count how many are below the threshold.
mask = A < N
sumBelowThreshold = nnz(mask)
% Get the values at the same locations in B.
% First as a list:
valuesBelowThreshold = B(mask)
% Then as a masked array
Bmasked = B .* mask

You'll see in the command window:

sumBelowThreshold =

8

valuesBelowThreshold =

14

13

40

59

29

14

66

72

Bmasked =

0 0 0 0 0

0 0 0 29 0

14 0 40 14 0

13 0 59 66 72

[Ilias Thanos]

Thanks! This works!

Answer 2

[Turlough Hughes]

This will show values of B that exist in A and which are also less than N.

result = B(ismember(B,A) & B<N)

If you need find the elements of B that exist in A within a certain tolerance there is also a function called ismembertol which will be appropriate in that case.

[Ilias Thanos]

Thanks for your answer! So i tried it and i entered for example N=800 but i got this answer:

result = [](0x0)

Any idea whats wrong?

[Turlough Hughes]

Well just looking at the data you provided, none of the values that are in B are in A that you provided above.

[Ilias Thanos]

Oh that's probably my bad cuz I wasnt clear enough. I'll edit the question. I want the program to show the B values that correspond to the A values less than N but more specific that correspond to their positions.

For example if the answer is 745 i want the program to show me 30 (see the matices above)

[Turlough Hughes]

Ah ok, no worries. I see what you mean now.