Sum only consecutive positive numbers and place the sum in a new vector in specific positions

Hi!

I have this variable P1 (attached) and i want to make the sum of ONLY consecutive positive values and place the sum in a new vector (out) in the position that you can see in Figure. In there is only one value you can place it in the same position of P1, otherwise, place it in the lowest consecutive positive position. For the other values of out i want zero.

I tried with this but it is not doing what i want...

Thanks in advance!!!

lo = P1 > 0;
h5 = cumsum(diff([0;lo(:)]) == 1).*lo(:);
out = accumarray(h5 + 1,P1);

[EM geo]

in order to make it easy I created a new question. @ darova

[darova]

thank you

Answer 1

[Thiago Henrique Gomes Lobato]

Try this:

lo = P1 > 0;
Dfference = diff([lo(:);0]); 
Ends  = find(Dfference==-1);  % -1 are the positions where a sequence ends
Start = find(Dfference==1)+1; %  1 are the positions where a sequence starts -1

% loop only over the founded sequences
out = zeros(size(P1));
for idx=1:length(Start)
    out(Ends(idx)) = sum(P1(Start(idx):Ends((idx))));
end

[EM geo]

that's perfect!! Thanks @Thiago Henrique Gomes Lobato

[EM geo]

Another question, sorry...if i want to place the sum in the positions 2-3-4-5 for the value 134.8250, positions 26-27-28-29 for value the 381.25 and in the positions 37-38-39-40 for the value 159.225 that you can see in Figure, how can i do? In other words, how can i repeat the sum for the 3 following positions?

Thanks in advance

@Thiago Henrique Gomes Lobato

[Thiago Henrique Gomes Lobato]

You have the sum result and also the index, so you just need to order them as you want. For your example it would be:

out(Ends(idx):Ends(idx)+3) = sum(P1(Start(idx):Ends((idx))));

For you to do this, however, you may have to make sure that the minimum distance between values is 3, as well as that there's no value for the last three entries of your array

[EM geo]

@Thiago Henrique Gomes Lobato I tried your code with different data, in which the first value is < -1. In this specific case the code doesn't work properly. In details, I get the matrix out equal to 0. I attached here the new data. Can you help me please?

[Thiago Henrique Gomes Lobato]

Works fine here, probably you missed something else in your code, check if you're using the right variables.

Excel = xlsread('dati_cortina.xlsx');
P1     = Excel(:,3);
lo = P1 > 0;
Dfference = diff([lo(:);0]); 
Ends  = find(Dfference==-1);  % -1 are the positions where a sequence ends
Start = find(Dfference==1)+1; %  1 are the positions where a sequence starts -1
% loop only over the founded sequences
out = zeros(size(P1));
for idx=1:length(Start)
    out(Ends(idx)) = sum(P1(Start(idx):Ends((idx))));
end
[P1,out]

   -3.0000         0
   -1.0000         0
    2.1000         0
    5.8000         0
    9.4000         0
   13.1000         0
   15.2000         0
   14.8000         0
   12.5000         0
    7.5000         0
    2.7000   83.1000
   -1.1000         0
   -3.0000         0
   -1.0000         0
    2.1000         0
    5.8000         0
    9.4000         0
   13.1000         0
   15.2000         0
   14.8000         0
   12.5000         0
    7.5000         0
    2.7000   83.1000
   -1.1000         0
   -3.0000         0
   -1.0000         0
    2.1000         0
    5.8000         0
    9.4000         0
   13.1000         0
   15.2000         0
   14.8000         0
   12.5000         0
    7.5000         0
    2.7000   83.1000
   -1.1000         0

[EM geo]

@Thiago Henrique Gomes Lobato

I'm sorry I uploaded the wrong file. Try with this file and with this code (your code completed with all your suggestions).

lo = P1 > 0;
Dfference = diff([lo(:);0]); 
Ends  = find(Dfference==-1);  
Start = find(Dfference==1)+1; 
SP = zeros(size(P1));
for idx=1:length(Start)
    SP(Ends(idx):Ends(idx)+3) = sum(P1(Start(idx):Ends((idx)))); % this is the part of code you missed in the previous answer
end 

However result are not right. As you can see the first data is has P1 > 0 so I expected to have out = 39 and repeat it for the following two rows.

This in an example of how results should be:

%P1	%out
39	39 %here P1 is >0 so i expect to have out =39
-2	39
-2	39
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
60	0
39	99  %here I have 60 and 39 that are >0, so i want their sum (99) placed here
-2	99
-2	99
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
60	0
39	99
-2	99
-2	99
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
-2	0
60	60

Thank you so much!!!!!!!!!

[Thiago Henrique Gomes Lobato]

Add those changes:

if length(Ends)>length(Start)
    Start = [Ends(1);Start];
end
SP = zeros(size(P1));
for idx=1:length(Start)
    End = min(Ends(idx)+2,length(P1));
    SP(Ends(idx):End) = sum(P1(Start(idx):Ends((idx)))); % this is the part of code you missed in the previous answer
end