what does the x(10:15) mean?

Hello everyone,

I am reading a code developed by someone else and don't understand what does the x(10:15).'*x(4:9).

I know that you can solve a set of variables by using a function and going like this: x(1) x(2) etc.

Here's the section of the code: y_hat = x(10:15).'*x(4:9);

How do you call that notation? x(10:15) so I can look it up and read about it in forums.

Thanks!

Answer 1

[Star Strider]

This assignment:

y_hat = x(10:15).'*x(4:9);

if ‘x’ is a row vector, does matrix multiplication of the transposed 5 elements of ‘x’ from ‘x(10)’ to and including ‘x(15)’ (to create a column vector) by the elements of ‘x(4:9)’ to create a matrix. If ‘x’ is a column vector, this calculated the dot product instead.

See the documentation on Array vs. Matrix Operations (link) for a relevant discussion.

[Torsten]

I think - depending on whether x is a row or column vector - y_hat is a 6x6 matrix or a scalar.

[Star Strider]

@Torsten — Oops! I did not see the transpose!

I revised my Answer accordingly.

Thanks!

Answer 2

[madhan ravi]

x(10:15)

it means elements from 10 to 15 are picked from vector x

see example:

>> x=1:15

x =

    Columns 1 through 13

       1     2     3     4     5     6     7     8     9    10    11    12    13

    Columns 14 through 15

      14    15

>> x(11:15)

ans =

      11    12    13    14    15

>>

[madhan ravi]

How do you call that notation?

its called as vector indexing