Matlab: change value of field of a struct inside an array

Question

I would like to know the Matlab way of doing this:

I have an array of structs (Line) called lines.

Each Line looks like:

point1: [1 128]
point2: [218 128]
 theta: -90
   rho: -127

I need to subtract a value from all the point1(2) and point2(2) of all the lines in struct.

Can you develop more about your struct. It like Line.point1 = Array 2x1 ? — Vuwox
– Vuwox, Commented Sep 26, 2013 at 20:02
This is a great candidate for generating a lines class, with a method to subtract a scalar from that element of that field. — chappjc
– chappjc, Commented Sep 26, 2013 at 20:05
Yes Alexander, If I write that on the console I get ans = 1 128. They are the X and Y coords of the point — fersarr
– fersarr, Commented Sep 26, 2013 at 20:05
Take into account that arrayfun may be slower than a for loop — Luis Mendo
– Luis Mendo, Commented Sep 26, 2013 at 20:40

chappjc · Accepted Answer · 2013-09-26 20:32:00Z

2

The one-line solution for point1 would use arrayfun and setfield/getfield as follows,

lineStructArray2 = arrayfun(@(x) (setfield(x,'point1',getfield(x,'point1')+[0 dy])), lineStructArray)

where dy is the value you want to add (negative for subtract) from point1(2). Make a similar command for point2.

answered Sep 26, 2013 at 20:22

chappjc

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Comments

Vuwox · Accepted Answer · 2013-09-26 20:14:37Z

0

If your array is made like this :

myArray = [line line2];

So you have a struct array. You can't acces it with

myArray(:).point1(2);

So you have to create a loop

myStoringArray = [];
for it = 1:size(myArray,2)
  myStoringArray = [myStoringArray myArray(it).point1(2)];
end

answered Sep 26, 2013 at 20:14

Vuwox

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And beware, a struct array must contain all same struct. So all your line need point1, point2, theta and rho define or at least set null.