error when calling a function inside of another function

2011 2 6
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I'm very new to matlab function. so sorry if i asked a stupid question. i got an error saying "The expression to the left of the equals sign is not a valid target for an assignment." for the line as:
answer = function2(x,y,z);
in function1. when I run another .m file which call this function1 and this function1 calls function2 like the above. I've tested the function2 at the command line with no error. which returns a (1,3) vector. and in function1, i didn't define the variable "answer". I tried to modify the function2 to make it return 3 output variable with each being a scalar and even reduce the function2 output to only one scalar output, it still gave the same error. could anybody give me some help? I really appreciate that.

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Walter Roberson
Walter Roberson 2011-2-6
Please show us the exact code line. There might be something subtle about what you used.

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Oleg Komarov
Oleg Komarov 2011-2-6

0 个投票

In orbit, line 16, you open a { and close } before the end, last line. Remove them.
Then variables r0 and a are not defined anywhere in the function.
Oleg

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newbie
newbie 2011-2-6

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ok, here is the function1 and the e_field() is the function2,thanks
function [pos_arr]=orbit(qom_in, pos, vel, dt)
x(1:3) = pos(1);
y(1:3) = pos(2);
z(1:3) = pos(3);
vx(1:3) = vel(1);
vy(1:3) = vel(2);
vz(1:3) = vel(3);
pos_arr = [];
ii = 1;
rad = sqrt(x(1)^2 + y(1)^2);
rho = sqrt((rad - r0)^2 + z(1)^2);
while((rad<(r0+a))&&(rad>(r0-a))&&(rho<a)){
e = e_field(x(1), y(1), z(1));
b = b_field(x(1), y(1), z(1));
ax(2:4) = ax(1:3);
ay(2:4) = ay(1:3);
az(2:4) = az(1:3);
vx(2:4) = vx(1:3);
vy(2:4) = vy(1:3);
vz(2:4) = vz(1:3);
x(2:4) = x(1:3);
y(2:4) = y(1:3);
z(2:4) = z(1:3);
ax(1) = qom_in*(e(1) + vy(1)*b(3) - vz(1)*b(2));
ay(1) = qom_in*(e(2) + vz(1)*b(1) - vx(1)*b(3));
az(1) = qom_in*(e(3) + vx(1)*b(2) - vy(1)*b(1));
vx(1) = vx(2) + (ax(1) + ax(2))*dt/2;
vy(1) = vy(2) + (ay(1) + ay(2))*dt/2;
vz(1) = vz(2) + (az(1) + az(2))*dt/2;
x(1) = x(2) + (vx(1) + vx(2))*dt/2;
y(1) = y(2) + (vy(1) + vy(2))*dt/2;
z(1) = z(2) + (vz(1) + vz(2))*dt/2;
ii =ii+1;
rad = sqrt(x(1)^2 + y(1)^2);
rho = sqrt((rad - r0)^2 + z(1)^2);
pos_arr = [pos_arr; [x(1), y(1), z(1)]];
}end

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