find ID's of repeated values in array

Let's say I have 2 arrays, one longer t1 (1x15 double) and a shorter one t2(1x8 double) and I tried to find the indices of t1 in the t2 as follows:

t1=[1,2,3,3,3,4,5,6];
t2=[1,1.5,2,3,4,5,6,7,8,9,9.5,19,25,31,42];
IDt1_int2=ismember(t2,t1)
>> ismember(t2,1)

ans =

  1×15 logical array

   1   0   1   1   1   1   1   0   0   0   0   0   0   0   0

but what I acutally wanted is something like this

IDt1_int2=find(ismember(t2,t1));

find(ismember(t2,t1))

ans =

     1     3     4     5     6     7

but what i want it to give as an ouput is an array of IDs which considers the numbeer 3 in my t1 three times like this

[1 3 4 4 4 5 6 7];

Could you help here? Thank you

[Stephen23]

The simple MATLAB approach:

t1 = [1,2,3,3,3,4,5,6];
t2 = [1,1.5,2,3,4,5,6,7,8,9,9.5,19,25,31,42];
[~,idx] = ismember(t1,t2) % note the order!

idx = 1×8

1 3 4 4 4 5 6 7

Don't waste your time calling ISMEMBER multiple times in an inefficient loop.

[Kim Arnold]

Thank you very much Stephen.

Yes I tried it with

[~,idx] = ismember(t2,t1)

which was the wrong order to give the inputs.

Answer 1

[Simon Chan]

You may use a for loop as follows:

idx = zeros(1,length(t1));
for k = 1:length(t1)
    idx(k) = find(ismember(t2,t1(k)));
end

[Kim Arnold]

Dear Simon,

Thanks that works perfectly fine!

Answer 2

[KSSV]

[c,ia] = ismember(t2,t1)

[Kim Arnold]

thank you, but this does not give me what I want as I described above it just gives me besides the logical also the location. but what I want is an output as: [1 3 4 4 4 5 6 7]; where it tells me that the number 3 of t1 is at position 4 in t2, three times because i need later to extract those positions again for plotting.

[Kim Arnold]

What you wrote was correct when it was first t1 and then t2 :) however, thank you for the input

[c,ia] = ismember(t1,t2)