MATLAB is giving me 0's instead of really small numbers
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I don't have code to share, but MATLAB is outputing 0's instead carrying through small numbers. When I change the command window to format long, the calculation show non zero. However, when my code runs it is carrying these zeros through my calculations.
>> Calculation
ans =
0.0
>> Format long
>> Calculation
ans =
8.425293911978570e-07
How do I make matlab keep the small numbers?
댓글 수: 2
Steven Lord
2021년 8월 18일
Can you show us a small segment of the code that appears to return 0's instead of the small numbers you expected?
How small is "really small" in this context? Smaller than realmin?
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Walter Roberson
2021년 8월 17일
MATLAB is keeping the small numbers throughout your calculation.
I recommend that you put
format long g
at the top of your code and run again.
댓글 수: 3
Walter Roberson
2021년 8월 18일
Your code might be zeroing the entire array at each step.
But as well, "format long g" does not affect the variable browser. There is a drop-down above the variable name that can select the format for the variable browser; personally though I recommend setting Preferences -> Variables -> Default Array Format to "long g", which controls the default format for the variable browser.
vikas singh
2023년 3월 12일
편집: Walter Roberson
2023년 3월 12일
I have written a code and it is giving me H3 and z2 zero. i dont know what is the problem.
clc;
clear all;
close all;
l=10000;
x=0:100:l;
t=[0;1;5;10;15;20;25];
H=30;
alpha=0.00384
Mu=2.8e-1;
D=31;
k=0.01132;
k1=l/H;
for n=1:100
a=2*H;
b=(1-(-1)^n*exp(-k*l))/((n*pi+(k^2*l^2)/(n*pi)));
c=1/(n*pi);
Cn(n)=a*(b-c);
end
s=0;
for n=1:100
d= sin(n*pi*x/l);
q= exp((-n^2*pi^2*t)/(Mu^2*l));
aa=Cn(n).*d.*q;
s=s+aa;
bb=(2*alpha*Mu^2*l^2)/(n*pi)^3;
s2=bb.*(1-q).*d;
end
J=(H+alpha*t).*x/l;
J1=alpha*t;
z1=s-s2-J+J1;
for n=1:100
syms X T
disp(n)
H0=(Cn(n)/(D-H)).*sin(n*pi*X).*exp(-n^2*pi^2*T/Mu)+(bb/(D-H)).*(1-exp(-n^2*pi^2*T/Mu)).*sin(n*pi*X) +(H/(D-H)+alpha*T*Mu*l/(D-H))*X+(H-alpha*T*Mu*l)/(D-H);
y=diff(H0*diff(H0,X),X);
Q=int(y*sin(n*pi*X),X,0,1);
P=int(Q*exp(n^2*pi^2*T/Mu),T,0,T);
Hn=-2*P/(exp(n^2*pi^2*T/Mu));
H1=Hn.*sin(n*pi*X);
for i=1:size(t,1)
H2=subs(H1,T,t/(Mu*l));
end
format long g
H3=subs(H2,X,x/l)
end
z2=double(((D-H)^2).*H3/l)
댓글 수: 22
Walter Roberson
2023년 4월 17일
Take the output of q4s in the code I show and do
output = subs(q4s, n, 1:100);
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