Menu
We all know the matlab colon operator to create a linear sequence, i.e.
1:5 = [1 2 3 4 5]
Now I found that the arguments of the colon operator can also be applied to vectors or matrices. However I do not understand the definition behind.
Examples
[1 2 3 4]:5 == [1 2 3 4 5]
[1 2; 3 4]:3 == [1 2 3]
Why is this?
The second argument can be vector or matrix as well.
Ultimately I would like to understand sequences such as
1:2:3:4:5
which is fully legal in matlab and [1 5] by the way!
Note 1:2:3:4:5:6 is left associative i.e. parsed as ((1:2:3):4:5):6.
So what is the behavior for the colon operator with matrix/vector arguments?
EDIT: corrected the statement of left associativity.
955
The colon is one of the most useful operators in MATLAB®. It can create vectors, subscript arrays, and specify for iterations. x = j : k creates a unit-spaced vector x with elements [j,j+1,j+2,...,j+m] where m = fix(k-j) . If j and k are both integers, then this is simply [j,j+1,...,k] .
The symbol colon ( : ) is used as an operator in MATLAB programming and is a commonly used operator. This operator is used to construct a vector that is defined by a simple expression, iterate over or subscribe to an array, or access a set of elements of an existing vector.
Colon operator (":") in R is a function that generates regular sequences. It is most commonly used in for loops, to index and to create a vector with increasing or decreasing sequence.
The colon operator, :, makes sequences of integers. For example, 4:7 creates the vector 〈4, 5, 6, 7〉. The combine function and the colon operator are used very often in R programming. The colon operator has precedence over basic arithmetical operators, but not over the power operator.
The documentation for the colon operator says:
If you specify nonscalar arrays, MATLAB interprets j:i:k as j(1):i(1):k(1).
Your first example is interpreted as 1:3, the second as 1:5
Expressions with more than two : are parsed left-associative:
a:b:c:d:e==(a:b:c):d:e
.
>> 1:2:3:4:5
ans =
1 5
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
