Matlab to C Code Function for Roundup

Hi, I am trying to create a function for C Code based on my Matlab function for rounding up a value to a user-defined variable.

I understand that you can use the Ceil function to round up when using printf, but as I am not displaying a lot of my calculations in the console I am looking for another method.

Below is an example of what I am trying to acheive:

Any help would be greatly appreciated!

% Function to round up a number to the specified decimal place
function return_value = ROUNDUP(value, decimalPlaces)
% Round the incoming value
count = 0;
magnitude = 1;
for count = 0 : decimalPlaces
magnitude = magnitude * 10;
end
return_value = ceil((value * magnitude) / magnitude);

<math.h> has a function called round.

C - round() function - fresh2refresh.com

As usual, "Structure" doesn't even bother reading the question.

Code:

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double roundUpDecimalPlaces(double x, int decimalPlaces) {
    double mag = 1.0;
    for (int i = 0; i < decimalPlaces; ++i)
        mag *= 10;
    return ceil(x * mag) / mag;
}

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Quote:

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Originally Posted by john.c

As usual, "Structure" doesn't even bother reading the question.

Code:

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double roundUpDecimalPlaces(double x, int decimalPlaces) {
    double mag = 1.0;
    for (int i = 0; i < decimalPlaces; ++i)
        mag *= 10;
    return ceil(x * mag) / mag;
}

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Thanks John. Im new to c code and curious how How does double x pick up the value and should int decimalPlaces be float decimalPlaces?

Thanks!

Quote:

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How does double x pick up the value

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You call the function with the initial value as that argument.

Quote:

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should int decimalPlaces be float decimalPlaces?

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Of course not, unless you say, have some notion of half a decimal place or 0.34 of a decimal place.

Well... a better approach:

Code:

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/* Changed 'decimalPlaces' to 'unsigned int' to avoid 'negative'
    values. Notice this value can still be very big, which will cause
    problems! Still. This argument is a count of decimal places, so
    it doesn't make any sense using a floating point type... */
double roundUpDecimalPlaces(double x, unsigned int decimalPlaces)
{
  double mag;

  /* Notice: 'decimalPlaces' will be converted to double when calling pow(). */
  mag = pow(10.0, decimalPlaces);   
  return ceil(x * mag) / mag;
}

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But, of course, keep in mind that floating point is accurate, but not exact in most cases.