Create for loop to simplify code and output arrays

I have this code:

len1 = a(4);
st1 = 5; % starting index for first channel
y1 = a(st1: st1+len1-1);

len2 = a(st1+len1);
st2 = st1+len1+1; % starting index for second channel
y2 = a(st2: st2+len2-1);
 
len3 = a(st2+len2);
st3 = st2+len2+1; % starting index for third channel
y3 = a(st3: st3+len3-1);
 
len4 = a(st3+len3);
st4 = st3+len3+1;% starting index for fourth channel
y4 = a(st4: st4+len4-1);

This is taking data from a text file and outputting different values for y (i.e y2 = 1524x1 double).

I know there's a simpler for loop I can do but I can't seem to get it right! Can you help?

Answer 1

[Esme Stanford-Durkin]

Solution, array to cell needed:

ch = a(1);
len = a(4);
st = 5 ; 
y{1} = a(st: st+len-1);

for i = 2 : ch 

    len(i) = a(st(i-1) + len(i-1 )); 
    st(i) = st(i-1) + len(i-1) + 1 ; 
    y{i} = a(st(i):st(i)+len(i)-1 ); 

end

Answer 2

[Saurav Roy]

Hey !

I think this is somwhat close to what you are looking for,

num = length(a);
len = a(4);st = 5;
y = a(st: st+num-1);

for i = 2 : num
    
       len(i) = a(st(i-1) + len(i-1));
       st(i) = st(i-1) + len(i-1) + 1;
       y(i) = a(st(i):st(i)+len(i)-1);
    
end

[Esme Stanford-Durkin]

Hey Saurav!

Thanks for the response. So num should be the number at index 1 of a so i've changed it to num = a(1). Not that that makes a difference (there's usually 4).

I've run your code and i get this error:

Unable to perform assignment because the left and right sides have a different number of elements.

Error in realdata_st (line 42)

y(i) = a(st(i):st(i)+len(i)-1 );

Here is the updated code:

num = a(1);
len = a(4);
st = 5 ; 
y = a(st: st+len-1);

for i = 2 : num 

    len(i) = a(st(i-1) + len(i-1 )); 
    st(i) = st(i-1) + len(i-1) + 1 ; 
    y(i) = a(st(i):st(i)+len(i)-1 ); 

end

Any ideas??

[Saurav Roy]

Hey,

what exactly does 'a' represent here ?

[Esme Stanford-Durkin]

a is an array containing all the data from the text file

a(1) is the number of 'channels' (number of y outputs), so in my initial code there would be 4 channels

a(4) contains the value of the length of the data

Then a(5) - a(5 + len-1) is the data

Then the next 'channel' will start.

If this makes sense

[Esme Stanford-Durkin]

Found the solution!

Answer 3

[Esme Stanford-Durkin]

a is an array containing all the data from the text file

a(1) is the number of 'channels' (number of y outputs), so in my initial code there would be 4 channels

a(4) contains the value of the length of the data

Then a(5) - a(5 + len-1) is the data

Then the next 'channel' will start.

If this makes sense