8.8: The Colon

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You can use the colon several ways in MATLAB (see help :). Its basic meaning is a vector of sequential values. For example, type

≫ x = 3:9

to get

x = 
   3 4 5 6 7 8 9

For increments other than 1, use statements like

≫ x = 1:0.5:4
≫ x = 6:-1:0

Most MATLAB functions will accept vector inputs and produce vector outputs. The statement

≫ y = sqrt(1:10)

builds a vector of integers from 1 to 10 and takes the square root of each of those numbers. Try it.

Now for another subtlety–what is the effect of each of the following statements and why?

≫ 1+1:5
≫ 1+(1:5)

Appending to a Matrix or Vector

A matrix or vector can be enlarged in size by appending new values to the old values. Let x=[1 3 5]:

\[\mathrm{x}=[\mathrm{x} 6810] \Rightarrow \mathrm{x}= [1356810] \nonumber \]

\[y=[x ; 1: 6] \Rightarrow y=\left[\begin{array}{llllll}
1 & 3 & 5 & 6 & 8 & 10 \\
1 & 2 & 3 & 4 & 5 & 6
\end{array}\right] \nonumber \]