check variable within 5% of a fixed value

checkp5=1;
while checkp5<2
if prms2>=pstd2*0.95
    if prms2<=pstd2*1.05
        P;
        Q;
        T;
        checkp5=2;
    else
        alphap=alphap*(pstd2/prms2);
        P=((E/(1+v))*a_barjk'*matrixp)/(a_barjk'*a_barjk+alphap*(c'*c));
        pmisfit=matrixp-((1+v)/E)*(a_barjk*P);
        prms2=(1/20)*sum(pmisfit.^2,'all');
    end
end
end

I need a code to check if prms2 is within 5% of pstd2(which is already fixed value) if not, P, pmisfit & prms2 will be recalculated until it falls within the 5% range

Answer 1

[Jan]

prms2 = inf;
limit = abs(pstd2) * 0.05;
while abs(prms2 - pstd2) < limit
  alphap  = alphap*(pstd2/prms2);
  P       = ((E/(1+v))*a_barjk'*matrixp)/(a_barjk'*a_barjk+alphap*(c'*c));
  pmisfit = matrixp-((1+v)/E)*(a_barjk*P);
  prms2   = (1/20)*sum(pmisfit.^2,'all');
end

Avoid lines, which do not perform anything like:

        P;
        Q;
        T;

Sometimes unnecessary parentheses are useful, if they clarify the intention. Spaces around operators can be nice. Compare:

  alphap  = alphap * pstd2 / prms2;
  P       = E / (1+v) * a_barjk' * matrixp / ...
            (a_barjk' * a_barjk + alphap * (c' * c));
  pmisfit = matrixp - (1 + v) / E * a_barjk * P;
  prms2   = sum(pmisfit .^ 2, 'all') / 20;