CODEWITHSUNDEEP
matlabindexingrangeincrement
user2100039
user2100039

Reputation: 1356

Increment MATLAB range

I'm not sure of an easier way to increment a range of numbers to use as an index to extract specific ranges in a series of numbers in a 12-number sequence. For example, I need an index to do the following:

Array1 is an array of 1 row by 612 columns. I need to create an index so that I"m extracting values 8,9,10,11 and 12 and then incrementing those by 12 so that the next columns I extract are 20, 21, 22, 23 and 24 and so forth to column == 612.

My index will look like this:

index = [ 8 9 10 11 12 20 21 22 23 24 32 33 34 35 36 ]

etc to 612.

I tried using something like index = [ 8:12:12:612] but it just gives me [ 8 20 32, etc].

Upvotes: 2

Views: 310

Answers (2)

Divakar
Divakar

Reputation: 221524

bsxfun based approach -

array1 = 8:12; %// Starting array
sz = 12; %// Stepsize

Ncols = floor((size(A,2)-array1(1))/sz)+1 %// No. of blocks of indices
ind1 = bsxfun(@plus,array1.',[0:Ncols-1]*sz) %//' Indices in blocks
index = ind1(ind1<=size(A,2)); %// Valid indices

Example -

A = rand(1,23); %// Random input for demo
array1 = 1:4; %// Starting array
sz = 8; %// Stepsize

Output -

index =
     1     2     3     4     9    10    11    12    17    18    19    20

Upvotes: 1

Luis Mendo
Luis Mendo

Reputation: 112659

Let

S = 12;  %// major step (minor step is 1)
G = 5;   %// group size
I = 8;   %// initial value
F = 612; %// ending value

Then the indices can be generated with this simple mod-based approach:

index = find(mod(0:F-1,S)<G)+I-1;

Upvotes: 0

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