sum in intervals from column!

Hi, after a long search for an answer, i give up!

I have a double vector: Index=[-1:0.1:1]

and a csv file (2 columns, one with 1/0 and the second column with indexes values)the rows different from file to another, looks like that:

N=

    1.0000    0.7810
    1.0000    0.7810
    1.0000    0.7810
    1.0000    0.7810
    1.0000    0.0240
    1.0000    0.7810
    1.0000    0.7810
         0   -0.8210
         0   -0.2620
         0   -0.8210
         0    0.0930
         0   -0.0920
         0   -0.8210
         0   -0.8210
         0   -0.0670
         0   -0.3760
         0   -0.8210
         0   -0.8210
         0   -0.8210
         0   -0.8210

i want to sum for each interval i.e: <-0.9, <-0.8 and so on.. the indexes (2nd column) for positive(1) and negatives(0) separately. not an accumulation sum, for <-0.8 it will be only for those who has -0.9<x<-0.8 etc.. that's what i tried to do:

[N T D] = xlsread('file.csv');
Index=[-1:0.1:1];
[r c]= size(N);
pos_idx= find(N(:,1)==1);
neg_idx= find(N(:,1)==0);

%first try
pos_count=accumarray(N(N(pos_idx,2)<Index'),[N(pos_idx,2)])

Error using < Matrix dimensions must agree.

%second try
A = accumarray(Index,[N(pos_idx,2)]',[],@(x) sum(x,'native'))

Error using accumarray Second input VAL must be a vector with one element for each row in SUBS, or a scalar.

%third try
count_p=sum([N(pos_idx,2)]'<Index)

Error using < Matrix dimensions must agree.

any idea where is the problem?? i tried to transpose the Index and the column, not success!!

thank's in advance :)

Answer 1

[Star Strider]

This seems to work:

binedg = [-1:0.1:1];
[Nh,edges,bin] = histcounts(N(:,2), binedg);
S = accumarray(bin, N(:,2));

If you don’t have histcounts, use:

[Nh,bin]= histc(N(:,2), binedg);

If all goes well, ‘S’ is your interval summaton vector corresponding to the intervals in ‘binedg’.

[Shayma]

histc works great!

thank you a lot :)

[Star Strider]

My pleasure!