i'm having issues using format short in my code

7 views (last 30 days)
Trevor Pixley on 18 Nov 2021
Commented: Trevor Pixley on 18 Nov 2021
I want to limit the number of decimal points my outputs have for an entire code section. I tried using "format short" at the top of my section, but find that my outputs at the end of calculations have 30+ digits attached. The values are correct, i just want to pare them down without having to use the vpa command on every one.
Trevor Pixley on 18 Nov 2021
Yeah for sure
here's what i'm running:
clear
clc
format short
syms t
E = 9000 %MPa
E = 9000
v = 0.36;
t = 152e-5;
I = eye(3);
F = t*[.1 -.171 0;
.063 .062 0;
0 -.045 -.149];
Ft = transpose(F);
strain = vpa(.5*(F+Ft),4);
rotation = vpa(.5*(F-Ft),4);
epskk = sum(diag(strain));
delta = 0;
for i = 1:length(strain)
for j = 1:length(strain)
if i==j
delta = 1;
else
delta = 0;
end
sig(i,j) = (E/(1+v))*(strain(i,j) + (v/(1-2*v))*epskk*delta);
end
disp(vpa(sig,4))
end   sigt = transpose(sig);
n = [0.8 -0.6 0];
nt = transpose(n);
T = vpa(sigt*nt,4);
signn = vpa(dot(T,n),4); %this is in MPa
T_normal = signn*nt
T_normal = T_shear = T-T_normal
T_shear = and the outputs are:
T_normal =
1.2462824873952785892947148942708
-0.93471186554645894197103617070313
0
T_shear =
0.018830117646986670192218298321815
0.025106823529315560256291064429087
0.13579411764699626557451077079207
as you can see, I've applied the vpa function to a lot of the calculations thru out the section already. I just want to know for the future if there's a different way to do this. I figure the issue is probably because I am doing this work with symbollic values before applying a number value for t, but can't confirm that this is overriding "format short".

Cris LaPierre on 18 Nov 2021
Because you are using symbolic variables. For symbolic, try using the digits function instead.
syms t
digits(4)
E = 9000; %MPa
v = 0.36;
t = 152e-5;
I = eye(3);
F = t*[.1 -.171 0;
.063 .062 0;
0 -.045 -.149];
Ft = transpose(F);
strain = .5*(F+Ft);
rotation = .5*(F-Ft);
epskk = sum(diag(strain));
delta = 0;
for i = 1:length(strain)
for j = 1:length(strain)
if i==j
delta = 1;
else
delta = 0;
end
sig(i,j) = (E/(1+v))*(strain(i,j) + (v/(1-2*v))*epskk*delta);
end
disp(sig)
end
1.1740 -0.5432 0 1.1740 -0.5432 0 -0.5432 0.7918 -0.2263 1.1740 -0.5432 0 -0.5432 0.7918 -0.2263 0 -0.2263 -1.3306
sigt = transpose(sig);
n = [0.8 -0.6 0];
nt = transpose(n);
T = sigt*nt;
signn = dot(T,n); %this is in MPa
T_normal = signn*nt
T_normal = 3×1
1.2463 -0.9347 0
T_shear = T-T_normal
T_shear = 3×1
0.0188 0.0251 0.1358
Trevor Pixley on 18 Nov 2021
that did it. thanks!

R2018a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!