MATLAB: Value of first derivative of Shape function at -1,0 and +1 using for loop?? Error using sym/diff (line 69) The second argument must be a variable or a nonnegative integer specifying the number of differentiations. Error in practise3 (line 29) N1=di

MATLAB

%%Shape function for axial effect
N1epsn=0.5*epsn^2-0.5*epsn; (ERROR HERE)
N2epsn=-1*epsn^2+1;
N3epsn=0.5*epsn^2+0.5*epsn;
for epsn=-1:1:1
    %%First Derivatives of Shape Function
    N1=diff(N1epsn,epsn)
    N2=diff(N2epsn,epsn)
    N3=diff(N3epsn,epsn)
end

Best Answer

%%Shape function for axial effect
syms epsn
N1epsn=0.5*epsn^2-0.5*epsn; 
N2epsn=-1*epsn^2+1;
N3epsn=0.5*epsn^2+0.5*epsn;
for epsn=-1:1:1
    %%First Derivatives of Shape Function
    N1=subs(diff(N1epsn),epsn) ;   
    N2=subs(diff(N2epsn),epsn) ;
    N3=subs(diff(N3epsn),epsn) ;
end
You should use double to convert sym to double.
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