How to round numbers on specific digits?

ROOT
#1

Hi,

I want to round given numbers to specific digits:
3.654 on digit 2 becomes 3.65
1.23456 on digit 4 becomes 1.2346
and so on.

I know that I could implement this by a function like

round_digits (double x, int y) { return (floor(x*10^y+0.5)/10^y); }
but I would like to know if something like this is already implemented in mathcore or mathmore?

liquidat

#2

It depends what you are trying to do. If you are printing something out, ‘Form’ or ‘sprintf’ is what you are looking for

char line[100];
sprintf (line, "%.2f", variable);
cout << line << endl;

or (preferably)

cout << Form(%.2f", variable);

If you are talking about rounding for doing calculations, the answer is more simple. You don’t. :smiley:

Cheers,
Charles

#3

Thanks for the answer - the intention was more a kind of sorting the data in a kind of histogram, but it then turned out the the whole approach was not well chosen.

I changed the code background and do not need a rounding any more (fortunately).

Nevertheless, thanks for the answer :slight_smile:

liquidat

#4

[quote=“liquidat”]Thanks for the answer - the intention was more a kind of sorting the data in a kind of histogram, but it then turned out the the whole approach was not well chosen.
[/quote]

This kind of situation is exactly where you do not want to round. :smiley:

Charles