i'm having issues using format short in my code

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.

[Adam Danz]

Could you provide a minimal working example?

[Trevor Pixley]

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".

Answer 1

[Cris LaPierre]

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]

that did it. thanks!