How do I remove elements of an array from another array?

Hi everyone! I would like to understand how to remove elements in an array. I post my code and then I explain my problem.

This is my code:

 for k = 1:size(allpoint_i,1)

    countP = ismember(Pp, allpoint_i(k,:),'rows');
    sumP(k) = sum(countP); %it counts how many times the point is first point of a segment
    countS = ismember(Sp, allpoint_i(k,:),'rows');
    sumS(k) = sum(countS); %it counts how many times the point is end point of a segment
        if ((sumP(k)+sumS(k))<=2) 

            %insert condition to remove that point both from Pp and Sp
            
        end
    
 end

I explain my problem. Let's start from the first element of allpoint_i. For the first element of allpoint_i I have sumP(1) = 1 and sumS(1)=1. So for the if statement, I have to remove that point from Pp and Sp. In Pp it occupies the 4th row, in Sp it occupies the first row and in addition, I would like to remove not only the 4th row of Pp and the first row of Sp, but also the 4th row of Sp and the first row of Pp. How can I do it? I attach a zip file containing the variables Pp, Sp, allpoint_i. Thanks in advance

[Dyuman Joshi]

"So for the if statement, I have to remove that point from Pp and Sp"

You want to remove the point in Pp and Sp whose value is equalto all_point(k), when the if condition is met?

[Loren99]

@Dyuman Joshi exactly!

[Dyuman Joshi]

Do you want to compare the whole row, or element from either row?

[Loren99]

@Dyuman Joshi the whole row

Answer 1

[Dyuman Joshi]

Try this -

r1=[];r2=[];
 for k = 1:size(allpoint_i,1)
    countP = ismember(Pp, allpoint_i(k,:),'rows');
    sumP(k) = sum(countP); %it counts how many times the point is first point of a segment
    countS = ismember(Sp, allpoint_i(k,:),'rows');
    sumS(k) = sum(countS); %it counts how many times the point is end point of a segment
        if ((sumP(k)+sumS(k))<=2) 
            %insert condition to remove that point both from Pp and Sp
            r1=[r1 find(sum(Pp==allpoint_i(k,:),2))'];
            r2=[r2 find(sum(Sp==allpoint_i(k,:),2))'];
        end
 end
Pp([r1 r2],:)=[];
Sp([r1 r2],:)=[];

[Loren99]

@Dyuman Joshi yeah I was thinking to something like this. However MATLAB gives me error in the line

r1=[r1 find(sum(Pp==allpoint_i(k,:),2))];

Error using horzcat

Dimensions of arrays being concatenated are not consisten

[Dyuman Joshi]

I have edited my answer. Do try it again.

[Loren99]

@Dyuman Joshi doing this I do not obtain errors and I obtain the row in which I am interested and that I want to remove from Pp and Sp. However I do not know how to remove it from Pp and Sp

for k = 1:size(allpoint_i,1)

    countP = ismember(Pp, allpoint_i(k,:),'rows');
    sumP(k) = sum(countP); %mi conta quante volte il punto i-esimo interno è primo punto di un segmento
    countS = ismember(Sp, allpoint_i(k,:),'rows');
    sumS(k) = sum(countS); %mi conta quante volte il punto i-esimo interno è secondo punto di un segmento
        if ((sumP(k)+sumS(k))<=2) %togli la riga corrispondente da Pp e da Sp
            rowp=find((Pp(:,1)==allpoint_i(k,1)) & (Pp(:,2)==allpoint_i(k,2)));
            rows=find((Sp(:,1)==allpoint_i(k,1)) & (Sp(:,2)==allpoint_i(k,2)));

        end
    
 end

For example, for k=723, I obtain an element for which sumP+sumS < = 2 . so I want to remove it from Pp and Sp. With my commands I obtain that the 723 element of allpoint_i occupies correctly the 776 row of Pp and the 777 row of Sp. How then can I remove from Pp the entire 776 row (first and second column) and from Sp the entire 777 row (first and second column) and then in addition remove from Pp also the 777 row (because of Sp) and from Sp also the 776 row (because of Pp). Please

[Dyuman Joshi]

I think you skipped over my last 2 lines of code.

%Deleting the rows
Pp([r1 r2],:)=[];
Sp([r1 r2],:)=[];