how to do a loop and call a function

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liyana nadirah
liyana nadirah 2020-2-9
评论： Stephen23 2020-2-10
function [g1]=func2(L,D,P,r,c,a,t)
g1=(((3*c)/(P*r))*((((D*(t-a))/L))-(L/6)));
end
function [g2]=func3(L,D,P,r,c,Y,t)
g2=1-((c/P)*exp(((-3*D)/(r*L))*(t-Y)));
end
hi guys. can someone help me? i have this to funtion and i have to set all the variable L,D,P,r,c,a and Y as a input and i have to do a for loop for t from 0 to 100 using this eqution and have to set the solution when a<t<=Y the it will use the first function and when t>Y it will use the second function and when t<a the fuction will be g=0 .but i don't know how to do it. so please help me
  2 个评论
Stephen23
Stephen23 2020-2-9
编辑：Stephen23 2020-2-9
"...i have to do a for loop for t from 0 to 100 ..."
Is it really required to use a loop? If the other parameters are scalar, it would be trivial to vectorize those functions.
"...but i don't know how to do it"
Use logical indexing:
https://www.mathworks.com/help/matlab/math/array-indexing.html

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回答（2 个）

David Hill
David Hill 2020-2-9
c=;
P=;
r=;
D=;
a=;
L=;
Y=;
t1=0:a;
t2=a+1:Y;
t3=Y+1:100;
g=[zeros(1,length(t1)),(((3*c)/(P*r))*((((D*(t1-a))/L))-(L/6))),1-((c/P)*exp(((-3*D)/(r*L))*(t3-Y)))];
t=0:100;
Stephen23
Stephen23 2020-2-9
编辑：Stephen23 2020-2-9
As described in the question, you will have to do something like this:
L = ???;
D = ???;
P = ???;
r = ???;
c = ???;
a = ???;
Y = ???;
t = 0:???:100;
%
N = numel(t);
g = zeros(1,N); % this already fulfills the t<a requirement.
for k = 1:N
if t(k)>Y
g(k) = func3(??????, Y, t(k));
elseif t(k)>a
g(k) = func2(??????, a, t(k));
end
end
I left a few trivial things for you to complete (you need to replace all of the ???).
Both functions will need to be saved somewhere where they are visible to this code.
  6 个评论
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liyana nadirah
liyana nadirah 2020-2-10
then what if i want to plot r from 0 to 1.42 and fix the t
Stephen23
Stephen23 2020-2-10
"then what if i want to plot r from 0 to 1.42 and fix the t"
If you only want to vary the r value then do the same like I showed you for L.
If you want to vary multiple different values then use ndgrid to generate all permutations.

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