How do you create an array around a central value?

I would like to write a function such as:

function [ array ] = generate_array( center_pt, resolution )

NB_POINTS = 5;

(...)

end

so that calling [ array ] = generate_array( 5, 2.5 )

array = [0 2.5 5 7.5 10]

Answer 1

[Star Strider]

How about this? It has three arguments, since I don’t know if you want the number of points to be an argument or decided by the function.

NrPts = 5;
CtrPt = 5;
Res   = 2.5;
generate_array = @(CtrPt,NrPts,Res) linspace(CtrPt-Res*fix(NrPts/2), CtrPt+Res*fix(NrPts/2), NrPts);

It generates the array you specified, and seems to be robust for other argument values.

[PR]

Thanks for your reply.

I would like the center point and resolution to be arguments and the number of points to always be 5 (hence the constant declaration).

Is there a for loop way that could be easier for me to grasp?

[Star Strider]

My pleasure.

If you always only want 5 points, my anonymous function becomes:

generate_array = @(CtrPt,Res) linspace(CtrPt-Res*2, CtrPt+Res*2, 5);

The linspace function is about as efficient as it is possible to get, and has been a part of MATLAB as long as I can remember. You could probably do this with a loop, but a simple colon-operator vector would seem to do as well, at least in the current application, although I cannot guarantee how robust it would be for other situations:

generate_array = @(CtrPt,Res) [CtrPt-Res*2 : Res : CtrPt+Res*2];

(The square brackets aren’t strictly necessary, but it improves the readability of the code. I know by looking at it that it is an array.)

I still prefer (and recommend) to use linspace because of its flexibility.

[PR]

Wow, ok! I can see now that linspace is the path of least resistance.

Everything remains contained in one line of code.

I have learned a great deal from your reply.

Many thanks

[Star Strider]

My pleasure! I very much appreciate your compliment.

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