Collect values into an array

I have the following within my code :

while time<tfinal

   for np = 1 : particleno 

   %Run Function to calculate guiding centre for diagnostic test

   [a, b, gcx]=guidingcentrefun(x1(np), x2(np), x3(np), y1(np), y2(np), y3(np));
end
end

Where guidingcentrefun is as follows:

function [ a b gcx] = guidingcentrefun(x1, x2, x3, y1, y2, y3)

%Calculate guiding centre with simultaneous eqns
k1=(-2*x1)+(2*x2);
k2=(-2*y1)+(2*y2);
k3=(x2^2) -(x1^2) + (y2^2) - (y1^2);
k4=(-2*x1)+(2*x3);
k5=(-2*y1)+(2*y3);
k6=(x3^2)-(x1^2)+(y3^2)-(y1^2);

%coordinates of guiding centre
b=((k1*k6)-(k3*k4))/((k1*k5)-(k2*k4));
a=(k3-(k2*b))/k1;

gcx = [ a ];
end

I just want gcx to store ALL of the values of a in one array. I can run the code and let the values of gcx be outputted so I know it all works:

gcx =1.1139

gcx =1.1146

gcx =1.1153

gcx =1.1159

gcx =1.1165

gcx =1.1170

gcx =1.1175

I know this is probably quite simple but i cant get it right and it is pretty urgent so help would be so much appreciated!! please! Thanks in advance! Phoebe

[Phoebe]

SORRY to clarify I have ONE particle the gcx in question is its x position moving along that changes as time progresses. SO that is why I cant have gcx(np) but gcx(time) does not work

[Image Analyst]

Then why does np go from 1 to particleno? Also, there is no time compute in the loop. I'll try your code attached below but I need to go out for a few hours. Post back if you end up fixing it on your own.

[Phoebe]

It is because I use the code to model multiple particles but I have to perform a calculation using a first. It is a particle pusher simulation so i use hundreds of particles but i have to calculate with the value for a first which is an x coordinate. What do you mean by no time compute?

Answer 1

[Image Analyst]

Try

for np = 1 : particleno 
   %Run Function to calculate guiding centre for diagnostic test
   [a, b, gcx(np)]=guidingcentrefun(x1(np), x2(np), x3(np), y1(np), y2(np), y3(np));
end

where you're adding an index, np, to the variable. The gcx in the main program is a separate variable from that in the called function, so it's okay to do it like this.

[Phoebe]

Hi i tried it so it looks like this;

[a, b, gcx(np)]=guidingcentrefun(x1(np), x2(np), x3(np), y1(np), y2(np), y3(np))

but letting the values output just still gives;

a =1.1170

b =0.2416

gcx =1.1170

a =1.1175

b =0.2419

gcx =1.1175 etc.

So still not an array!?!?

[Image Analyst]

Seems strange. It worked fine for me. Try my exact code (save it in a file called "test2.m"):

function test2
particleno = 10;
% Sample data:
x1 = rand(1,particleno);
x2 = rand(1,particleno);
x3 = rand(1,particleno);
y1 = rand(1,particleno);
y2 = rand(1,particleno);
y3 = rand(1,particleno);

for np = 1 : particleno  
  %Run Function to calculate guiding centre for diagnostic test  
  [a, b, gcx(np)] = guidingcentrefun(x1(np), x2(np), x3(np), y1(np), y2(np), y3(np))
end
plot(gcx);

function [a, b, gcx] = guidingcentrefun(x1, x2, x3, y1, y2, y3)
%Calculate guiding centre with simultaneous eqns
k1=(-2*x1)+(2*x2);
k2=(-2*y1)+(2*y2);
k3=(x2^2) -(x1^2) + (y2^2) - (y1^2);
k4=(-2*x1)+(2*x3);
k5=(-2*y1)+(2*y3);
k6=(x3^2)-(x1^2)+(y3^2)-(y1^2);

%coordinates of guiding centre
b=((k1*k6)-(k3*k4))/((k1*k5)-(k2*k4));
a=(k3-(k2*b))/k1;

gcx = a;

[Phoebe]

Yours works great! I will attach my code and the relevant function files to let it run if you can see what it happening to stop it working? please?

The stuff that is relevant is probably on lines 80 to 85 ??

This would be SO much help!

[Phoebe]

Sorry to clarify ParticlePusherNEW is the main script file all others are Function files so the line reference 80-85 is for ParticlePusherNEW