How create a matrix that matches a condition in comparison with other matrix?

The matrix A is given by several repeated values of A(:,1) positions with different A(:,2) values like:

clc;clear all
A=[
1   10
1   9
1   8
1   7
1   6
2   15
2   14
2   13
2   12
2   11
3   18
3   17
3   16
3   15
3   14
4   12
4   11
4   10
4   9
4   8];
scatter(A(:,1),A(:,2),'filled','r')

Represented by the following red dots:

The matrix B, represents 1 [X,Y] combination for each B(:,1) as:

%%
B=[
1   8
2   14
3   11
4   12];
 
hold on
scatter(B(:,1),B(:,2),'filled','b')

How can I eliminate all the values extrictly higher than any B(:,2) for each B(:,1) and keep only same or lower values getting a C matrix like:

%%
C=[
1   8
1   7
1   6
2   14
2   13
2   12
2   11
4   12
4   11
4   10
4   9
4   8];
scatter(C(:,1),C(:,2),'filled','g')

green dots represent the wanted points to keep.

Answer 1

[Adam Danz]

A=[
1   10
1   9
1   8
1   7
1   6
2   15
2   14
2   13
2   12
2   11
3   18
3   17
3   16
3   15
3   14
4   12
4   11
4   10
4   9
4   8];

B=[
1   8
2   14
3   11
4   12];

idx =  cell2mat(arrayfun(@(i){A(:,1)==B(i,1) & A(:,2)<= B(i,2)},1:size(B,1))); 
[rowIdx,~] = find(idx);
C = A(rowIdx,:)

C = 12×2

1 8 1 7 1 6 2 14 2 13 2 12 2 11 4 12 4 11 4 10

●

[Philippe Corner]

It seems that Index functions make easier our matrix manipulations rather than loops. Thanks a lot Adam.

[Adam Danz]

Loops aren't a bad thing but indexing is usually much more efficient.

Glad I could help.

[Philippe Corner]

Hello Adam, could you check this question? I think you may help me to find the best way to solve it.. https://it.mathworks.com/matlabcentral/answers/894752-how-to-assign-values-to-a-mesh-based-on-xyzc-points

[Adam Danz]

I commented on the thread.