Function to chop a decimal to a variable number of digits

I wrote the following function to approximate a number using chopping arithmetic.

chop(5,4.333352312) 

function output = chop(numdigits,float)

y = floor(log10(float)+1); %number of digits in the integer part 

x = fix(numdigits - y); 

fprintf("%.xf",float) 
end

The function is meant to approximate a float using numdigits chopping arithmetic. Since that is a variable, the number of digits after the decimal point is unknown. The output in the above example should be 4.3333 but the output is 4e+00. Is there any alternate way to display a variable number of digits after the decimal point?

Answer 1

[Stephen23]

You can use an asterisk * to refer to an input of fprintf, so in your case all you need is:

fprintf("%.*f\n",x,float);

and tested:

>> chop(5,4.333352312)
4.3334

Of course if you want to return that string as an output argument you will need to use sprintf instead:

function s = chop(numdigits,float)
y = floor(log10(float)+1);
x = fix(numdigits - y);
s = sprintf("%.*f",x,float);
end

[Aleem Andrew]

Thank you for your help

Answer 2

[Ameer Hamza]

MATLAB does not recognize what does 'x' means inside fprintf() function call. Try the following code

chop(3,4.333352312) 
function chop(numdigits,float)
    y = floor(log10(float)+1); %number of digits in the integer part 
    fprintf(sprintf('%%%d.%df', numdigits+1, numdigits-y), float);
end