# Selecting specific values from an array based on a defined condition

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SB on 25 Sep 2019
Commented: SB on 25 Sep 2019
I have the following array:
d = [0,100,-100];
m = 300;
I want to select certain values of array d as follows:
d(0<=m+d<=300);
So i want to select all the d values where m+d is beween 0 and 300 with both ends included. The result should look like [0,-100] and 100 should be excluded since it is out the defined range. However, I am getting d to be [0,100,-100]. Please let me know where I went wrong.

Fabio Freschi on 25 Sep 2019
Edited: Fabio Freschi on 25 Sep 2019
d+m is not scalar: use a single & for logical AND
d(d+m >= 0 & d+m <= 300)

#### 1 Comment

SB on 25 Sep 2019
Thank you!

Johannes Fischer on 25 Sep 2019
Edited: Johannes Fischer on 25 Sep 2019
Th logical expression
0 <= m+d <= 300
is not interpreted by Matlab as you think it is. It rather is interpreted as
(0 <= m+d) <= 300
where the expression in brackets results in logical 0 and 1 values which all are below 300, which in turn results in logical 1 at each position. What you want is a combination of both cases
d(0 <= m+d && m+d <= 300);

SB on 25 Sep 2019
I actually tried that. It gives me the following error:
Operands to the || and && operators must be convertible to logical scalar values.
Johannes Fischer on 25 Sep 2019
You are right, only one '&' is necessary
d(0 <= m+d & m+d <= 300);
SB on 25 Sep 2019
Thank you.