Hi,
I have created an array of structures for the x, y, and z coordinates of particles at time t. For example, suppose I have 3 particles and monitor the positions of the particles at five different times:
s(1).x=1.1:0.1:1.5;
s(1).y=2.1:0.1:2.5;
s(1).z=3.1:0.1:3.5;
s(2).x=4.1:0.1:4.5;
s(2).y=5.1:0.1:5.5;
s(2).z=6.1:0.1:6.5;
s(3).x=7.1:0.1:7.5;
s(3).y=8.1:0.1:8.5;
s(3).z=9.1:0.1:9.5;
For the purpose of this example, I have just made up the x, y, and z coordinates of the three particles at the five times. (My actual data is much more extensive; it contains information about 254 atoms at 2001 different times, but my structure organization is the same.)
Now suppose that I want to find the displacement of the ith particle at time t relative to its position at the first time. For this, I have written a function called delta:
function result = delta(i,t,structureName)
xvalinitial=structureName(i).x(1);
yvalinitial=structureName(i).y(1);
zvalinitial=structureName(i).z(1);
xval=structureName(i).x(t);
yval=structureName(i).y(t);
zval=structureName(i).z(t);
result=[xval-xvalinitial yval-yvalinitial zval-zvalinitial];
So if I call for example delta(1,2,s), I get the displacement of atom 1 at time 2, relative to atom 1's initial position:
>> delta(1,2,s)
ans =
0.1000 0.1000 0.1000
But, now, what if I wanted to vectorize my function delta? What if I wanted to be able to "map" delta across a vector. For example, ideally, I would like to be able to type:
and obtain a list of the displacements of atoms 1, 2, AND 3 at time 2 relative to the initial time, time 1.
Or, I might want to be able to type:
and obtain a list of the displacement of atom 1 at the time 2 AND at the time 3, relative to the initial time, time 1.
(By "list," I guess I really mean "matrix" or "array", where each row contains x, y, and z coordinates for the delta of the atom(s) at the time(s).)
Can you please help me see how I might be able to write the delta function so that I am able to do this? Should I be using the built-in Matlab command structfun? I tried this, but I have not had success so far. Is there any other way that I can "map" my delta function across vectors?
Thanks in advance. Andrew DeYoung Carnegie Mellon University
