I have problem with simplifing my equation

Dear all

i have cod like below :

clc
clear all
a=1;
m=9;
u=[3.8317   7.0156  10.1735  13.3237  16.4706  19.6159  22.7601    25.9037   29.0468 ];
syms r
for j=1:m
    for i=1:100;
        yy1(i)=(((-1)^(i-1))/((factorial(i-1))*(factorial(i))))*(((u(j))*r)/2)^(2*(i-1)+1) ;
    end
    YY1(j)=sum(yy1);
    jj1(j)=eval(YY1(j));

end

answer give me :

jj1 =
[ NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN]

even if i make :

r=1
eval(jj1)

again :

eval (jj1)
ans =
 Columns 1 through 8
NaN   NaN   NaN   NaN   NaN   NaN   NaN   NaN
Column 9
NaN

but when i run this cod :

clc
clear all
for i=1:100;
    y1(i)=(((-1)^(i-1))/((factorial(i-1))*(factorial(i))))*(z/2)^(2*(i-1)+1) ;
end
Y1=sum(y1);
z=1;
eval(Y1)

answer give me :

ans =

    0.4401
    
    

they only different at Fixed coefficient

u(j)/2

Answer 1

[Walter Roberson]

Works for me.

a=1;
m=9;
u=[3.8317   7.0156  10.1735  13.3237  16.4706  19.6159  22.7601    25.9037   29.0468 ];
R = 1;
syms r
jj1 = zeros(1,m);
YY1 = zeros(1,m,'sym');
for j=1:m
    yy1 = zeros(1,100,'sym');
    for i=1:100
        yy1(i)=(((-1)^(i-1))/((factorial(i-1))*(factorial(i))))*(((u(j))*r)/2)^(2*(i-1)+1) ;
    end
    YY1(j)=sum(yy1);
    jj1(j) = double(subs(YY1(j), r, R));
end

You should never eval() a symbolic expression.

eval() of a symbolic expression is equivalent to eval(char()) of the expression. However, char() of a symbolic expression is not generally a MATLAB expression.

>> char(repmat(sym('x'),[2 2 2]))
ans =
    'array(1..2, 1..2, 1..2, (1, 1, 1) = x, (1, 1, 2) = x, (1, 2, 1) = x, (1, 2, 2) = x, (2, 1, 1) = x, (2, 1, 2) = x, (2, 2, 1) = x, (2, 2, 2) = x)'

char() of a symbolic expression is also not generally a MuPAD expression.

[shahin hashemi]

tanx alot walter for ur answer

[shahin hashemi]

hi again walter

i have small quastion and i really appreciated if u could help me

a=1;
m=9;
u=[3.8317   7.0156  10.1735  13.3237  16.4706  19.6159  22.7601    25.9037   29.0468 ];
R = 1;
syms r
jj1 = zeros(1,m);
YY1 = zeros(1,m,'sym');
for j=1:m
    yy1 = zeros(1,100,'sym');
    for i=1:100
        yy1(i)=(((-1)^(i-1))/((factorial(i-1))*(factorial(i))))*(((u(j))*r)/2)^(2*(i-1)+1) ;
    end
    YY1(j)=sum(yy1);
end

do u think is it possible to use integral (numerical integration) base on r

for YY1 ?

and consider r for 0:1

and can u plz help me with the code and do you think the answer is relaible ?

tanx again