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How do I convert fractional display to decimal display ?

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Ibrahim A
Ibrahim A on 22 Mar 2021
Commented: Steven Lord on 22 Mar 2021
I am getting bunch of fractional values in my output matrix and I have other matrixes outputting the same way as this one. I cannot find a way to change it to decimal notation, something like 1.678.

Accepted Answer

Steven Lord
Steven Lord on 22 Mar 2021
Call double or vpa on your symbolic variable.
Steven Lord
Steven Lord on 22 Mar 2021
two = sym(2);
sqrt2 = sqrt(two)
sqrt2 = 
V = vpa(sqrt2)
V = 
D = double(sqrt2)
D = 1.4142
whos two sqrt2 V D
Name Size Bytes Class Attributes D 1x1 8 double V 1x1 8 sym sqrt2 1x1 8 sym two 1x1 8 sym
V, sqrt2, and two are all sym. So in the code below the line assigning to f(t) creates a symbolic function:
syms t
f(t) = V
f(t) = 
D is a double. In the code below assigning to g(t) attempts to store D in element t of the array g.
g(t) = D
Error using sym/subsindex (line 864)
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym expression.
qdd(t) = V % works
qdd(t) = D % errors

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More Answers (1)

Bjorn Gustavsson
Bjorn Gustavsson on 22 Mar 2021
You might have set format to rat somewhere, perhaps in a startup.m or the like. You could get back to more normal decimal output by something like this:
format short g
For additional options check the help and documentation to format.
  1 Comment
Ibrahim A
Ibrahim A on 22 Mar 2021
Unfortunately, didn't work. I also tried to change the format on preferences -> matlab -> command window -> numeric format (Short g, compact), that also didn't work. I should also mention that I am using symbolic math toolbox, I don't know if it is related or not. But thank you for your answer.

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