# calculate integration of function

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Commentato: Star Strider il 14 Ago 2023
clc
clear
syms x y z D L B A(m, n, j, t) R
nfin = 1; nffin = 3; % length of summation of n
jfin = 1; jffin = 3; % length of summation of j
mfin = 1; mffin = 3; % length of summation of m
rowmat = [0];
for kk1=nfin:nffin
for kk2 = jfin:jffin
for kk3 = mfin:mffin
rownew = A(kk1, kk2, kk3, t)*sin(kk1*pi*x)*cos(kk2*pi*D*y/L)*cos(kk3*D*pi*z/B);
rowmat = [rowmat rownew];
end
end
end
Phiterms = rowmat(2:end);
Phi = sum(Phiterms.')
size(Phiterms)
diff(Phi,y,2)+diff(Phi,z,2)),t,1)+diff(diff(Phi,y,1),x,1)*(diff(diff(Phi,y,1),x,2)+diff(diff(Phi,y,1),y,2)+diff(diff(Phi,y,1),z,2))+diff(diff(Phi,z,1),x,1)*(diff(diff(Phi,z,1),x,2)+diff(diff(Phi,z,1),y,2)+diff(diff(Phi,z,1),z,2))-(diff(Phi,y,2)+diff(Phi,z,2))*(R+(diff(diff(Phi,x,1),x,2)+diff(diff(Phi,x,1),y,2)+diff(diff(Phi,x,1),z,2)))==diff(Phi,x,4)+diff(Phi,y,4)+diff(Phi,z,4)
Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.
colmat=[];
for kk1=nfin:nffin
for kk2=mfin:mffin
for kk3=jfin:jffin
colnew1 = int(ans*sin(kk1*pi*x), 0, 1);
colnew2 = int(colnew1*cos(kk2*pi*y*D/L), 0, L/D);
colnew3 = int(colnew2*cos(kk3*pi*z*D/B), 0, B/D);
colmat = [colmat; colnew3];
end
end
end
Phi_terms = colmat(2:end);
Phi_ = sum(Phi_terms);
size(Phi_terms)
##### 1 CommentoMostra -1 commenti meno recentiNascondi -1 commenti meno recenti
Dyuman Joshi il 13 Ago 2023
You have undefined variables in your code - m, n, j, and t.
Also, please explain what you are doing here, what is the objective and what error/problem you are facing.

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### Risposte (1)

Star Strider il 13 Ago 2023
This term, near the beginning of what I call ‘EXPR’
diff(Phi,y,2)+diff(Phi,z,2),t,1)+ ...
needs an extra diff call:
diff(Phi,y,2)+diff(diff(Phi,z,2),t,1)+ ...
then it works.
Beyond that, it’s not obvious what this code does, however with that change (even though you do not appear to do anything with that value) the code runs without error —
syms x y z D L B A(m, n, j, t) R
nfin = 1; nffin = 3; % length of summation of n
jfin = 1; jffin = 3; % length of summation of j
mfin = 1; mffin = 3; % length of summation of m
rowmat = [0];
for kk1=nfin:nffin
for kk2 = jfin:jffin
for kk3 = mfin:mffin
rownew = A(kk1, kk2, kk3, t)*sin(kk1*pi*x)*cos(kk2*pi*D*y/L)*cos(kk3*D*pi*z/B);
rowmat = [rowmat rownew];
end
end
end
Phiterms = rowmat(2:end);
Phi = sum(Phiterms.')
Phi =
size(Phiterms)
ans = 1×2
1 27
EXPR = diff(Phi,y,2)+diff(diff(Phi,z,2),t,1)+diff(diff(Phi,y,1),x,1)*(diff(diff(Phi,y,1),x,2)+diff(diff(Phi,y,1),y,2)+diff(diff(Phi,y,1),z,2))+diff(diff(Phi,z,1),x,1)*(diff(diff(Phi,z,1),x,2)+diff(diff(Phi,z,1),y,2)+diff(diff(Phi,z,1),z,2))-(diff(Phi,y,2)+diff(Phi,z,2))*(R+(diff(diff(Phi,x,1),x,2)+diff(diff(Phi,x,1),y,2)+diff(diff(Phi,x,1),z,2)))==diff(Phi,x,4)+diff(Phi,y,4)+diff(Phi,z,4)
EXPR =
colmat=[];
for kk1=nfin:nffin
for kk2=mfin:mffin
for kk3=jfin:jffin
colnew1 = int(ans*sin(kk1*pi*x), 0, 1);
colnew2 = int(colnew1*cos(kk2*pi*y*D/L), 0, L/D);
colnew3 = int(colnew2*cos(kk3*pi*z*D/B), 0, B/D);
colmat = [colmat; colnew3];
end
end
end
Phi_terms = colmat(2:end);
Phi_ = sum(Phi_terms);
size(Phi_terms)
ans = 1×2
1 53
.
##### 2 CommentiMostra NessunoNascondi Nessuno
Thanks.
Star Strider il 14 Ago 2023
My pleasure!
.

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