It seems that your ‘beta’ values are actually z-scores, since the standard normal distribution requires two parameters, those being the mean and standard deviation. For the z-score, those are taken to be 0 and 1, respectively, since the z-score normalizes them.
This could be what you want:
Pf = normcdf(beta)
or perhaps:
Pf = normcdf(-beta)
or using the core MATLAB erf function:
Phi = @(beta) (1- erf(beta/sqrt(2)))/2;
Pf = Phi(beta)
Pf = Phi(-beta)
Without more information, it is difficult to determine the exact solution to your problem. See the documentation on Find Cumulative Distribution Function of Normal Distribution (link). The argument to the erf function in that section would be your ‘beta’ values.
That is my best guess.
