Mathscript - modeling Z(x,y)

Question

Although a LabVIEW veteran, I am just starting working with mathscript window (and node).  I did some playing today but need to know the proper way to model uncertainty in a process that I am doing.  Ultimately, the uncertainty (z4) is a function of two variables (twotau and deltat) in the following script - therefore I expect to generate a 3d surface graph with z4, twotau, and deltat on the Z, X, and Y axes, respectively.  Here is the script.  How do I specify the range for twotau and deltat so that this script will run.  Thanks for your help......Don
SR=6.4;
v=0.029;
a=(1/(2*SR));
c=0.02997055434;
z1=-c/(twotau);
z2=c*deltat/(twotau)^2;
z3=sqrt((z1^2)*(a^2)+(z2^2)*(a^2));
z4=(z3/v)*100;

Answer 1

Hello Don,
You state in your first reply that you did not concentrate on the matrix versus non-matrix calculations.  Unfortunately, this was the cause of the first error message you received.  Line 8 reads
z1 = -c/twotau;
This tries to divide a scalar by a matrix and it is not a defined operation.  By adding a period to the operation, you tell LabVIEW MathScript to perform a scalar division (i.e. elementwise).  You did add the periods in your second reply and got a different error later in the script.  If you run your script in the MathScript Window and look at the variable values after execution, you can see that we are trying to generate a surface plot with xx and yy (both 100x100 matrices) and z4 (a 1x100 matrix).  These are the incompatible sizes the error is informing you of.  You got off to the right start using the meshgrid function to generate the matrices corresponding to twotau and deltat.  However, you then need to use these matrices in any computation of 2D matrices.  Your script continued to use deltat and twotau in the computation of the z matrices.  Instead of using xx for twotau and yy for deltat, I'll use tt and dt, respectively.  If you change your code to the following, it should work fine.
[tt dt] = meshgrid(twotau, deltat);
z1=-c./tt;
z2=c.*dt./tt.^2;
Of course, you'll also need to change your surf command to be
surf(tt, dt, z4)
Grant M.
Staff Software Engineer | LabVIEW Math & Signal Processing | National Instruments