How to write a vector-valued function with vector input from the screen in MATLAB?

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jack
jack 2017-12-16
回答： jack 2017-12-21
I am trying to do the following in MATLAB:
1. input *from screen* a small positive integer M (between 1 and 8);
2. input *from screen* M function expressions with variables `t, x1, x2, ... xM`; name for now these M functions f1,f2,...,fM;
3. given a vector `v=[t,x1,x2,...,xM]`, evaluate each of the M functions with the input `v`;
4. the output is a vector `Y=[y1,y2,...,yM]` where `y1=f1(v),y2=f2(v),...`.
I learned from this [old code][1] that I can do (1) and (2) with
TRUE = 1;
FALSE = 0;
OK = FALSE;
while OK == FALSE
fprintf(1,'Input the number of equations\n');
M = input(' ');
if M <= 0 | M > 7
fprintf(1,'Number must be a positive integer < 8\n');
else
OK = TRUE;
end;
end;
ss = cell(M,1);
for I = 1:M
fprintf(1,'Input the function F_(%d) in terms of t and y1 ... y%d\n', I,M);
fprintf(1,'For example: ''y1-t^2+1'' \n');
kk = input(' ');
ss{I} = kk;
end;
How can I do (3) and (4)?
[1]: https://www.mathworks.com/matlabcentral/answers/uploaded_files/97690/ALG057.m

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采纳的回答

jack
jack 2017-12-21
I have just found that (3) and (4) can be done by the following code
TRUE = 1;
FALSE = 0;
OK = FALSE;
while OK == FALSE
fprintf(1,'Input the number of equations\n');
M = input(' ');
if M <= 0 || M > 7
fprintf(1,'Number must be a positive integer < 8\n');
else
OK = TRUE;
end
end
ss = cell(M,1);
for I = 1:M
fprintf(1,'Input the function F_(%d) in terms of t and y1 ... y%d\n',...
I,M);
fprintf(1,'For example: ''y1-t^2+1'' \n');
kk = input(' ');
ss{I} = kk;
end
%(3)
V = 1:M+1; %replacing V with other input vectors here
c = num2cell(V);
Y = zeros(1,M);
if M==1
ysym = sym('y1');
else
ysym = sym('y%d',[1,M]);
end
syms t
for I = 1:M
z = evalin(symengine, ss{I});
f = symfun(z,[t,ysym]);
Y(I)=f(c{:});
end
%(4)
Y

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