problem with subs function

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Mariam Yehia
Mariam Yehia 2017-4-21
评论： Walter Roberson 2017-4-21
hello here is my program....it substitutes the value for the first run only; then the symbols appear again!
syms La Lb Lc
Ia=(20+6*La+.02*La^2);
Ib=(25+5.5*Lb);
Ic=(20+6.5*Lc+.005*Lc^2);
IHRa=diff(Ia,La)
IHRc=diff(Ic,Lc)
for L=0:10:90
if L<=30
Lb=L
else
Lb=30;
b=L-Lb
ihr_a=subs(IHRa,La,b)
ihr_c=subs(IHRc,Lc,b)
p=ihr_a-ihr_c
end
end
  1 个评论
Walter Roberson
Walter Roberson 2017-4-21
When I try, I appear to get substituted values each time.
I am not sure what you mean by "the first run". Your "if L<=30" statement is true for L = 0, 10, 20, and 30, and in those cases the only action you request is Lb=L .
Perhaps your "end" for your "if" is too late? Should it be
for L=0:10:90
if L<=30
Lb=L
else
Lb=30;
end
b=L-Lb
ihr_a=subs(IHRa,La,b)
ihr_c=subs(IHRc,Lc,b)
p=ihr_a-ihr_c
end

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