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# How can we precise the substituted values (to 04 numbers )after differentiation?

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Closed: MATLAB Answer Bot on 20 Aug 2021
I have differentiated the polynomial equation and have substituted the values to the variables. But I need to precise the values. Can any one please provide with answer?

Maitreyee Mordekar on 8 Aug 2016
I assume that you are using MATLAB 2016a version. I have a small code snippet that I think is your concern.
syms x;
y=x.^3;
z=diff(y,1);
x1=3.0912345678;
z1=subs(z,x1);
This would display the z1 as a fraction. Just convert the z1 variable to a floating number precision. You may use single or double point precision.
z2=single(z1); %Single precision
z3=double(z1); %Double precision
This should return the result in a numeric format with the precision according to the double or single data type.
In case you can afford to stay in the symbolic domain, you may use the variable-precision arithmetic. The result will be a symbolic data and not a numeric one.
z4 = vpa(z1,10);
You may refer to variable precision arithmetic for the documentation.
Hope it helps.