setting decimal points

Programming Questions

archi_stu..

in Programming Questions • 2 years ago

hello, does anyone know how to set a maximum decimal point without using nf()?

thanks

Replies(9)

PhiLho

Re: setting decimal points

2 years ago

What is a "maximum decimal point"? It is a decimal point with super powers?
Perhaps you should explain more in detail what you are trying to achieve, instead.

archi_stu..

Re: Re: setting decimal points

2 years ago

it is the maximum number of digits after the decimal point

nardove

Re: setting decimal points

2 years ago

Not sure if this is what you're after but try:

float x = 100.12345678;
float truncate( float x ) {
return round( x * 100.0f ) / 100.0f;
}
println( truncate( x ) );

Will output 100.12

If you need 3 decimals just change 100.0f to 1000.0f

Hope that helps

archi_stu..

Re: setting decimal points

2 years ago

thank you nardove. i did it a really round about way but it doesnt seem to always work. trying to figure out the reason...

float sum = 100.12345678;
int i = int(sum);
float k = sum - i;
String kk = nf(k, 0,2);
float kkk = float(kk);
float newsum = kkk + i;
println(newsum);

sometimes it gives 2 decimal, but sometimes i gives me a 'nearly there' like 1.9999997

PhiLho

It might come as a shock to you, but floating point numbers used in computing are of limited precision, so rounding errors like the one you report are quite common. You live with them, or compensate them.

archi_stu..

Re: Re: setting decimal points

2 years ago

thanks phil, ive learnt a lot today.

although, when i think about it, the method i used didnt round it, i cropped the decimal place away with nf() function... hmmmm

so theoretically, it should have worked perfectly.. unless there is a flaw i havent thought of yet

PhiLho

Re: setting decimal points

2 years ago

Take a step back and think why you need to round or crop extra decimals. In most cases I can think of, this isn't just not necessary, and can just hurt precision. In general, you do this limitation when you need to output the data, to screen or to a file. Then, you need the data as a string, and thus you use nf().

archi_stu..

Re: Re: setting decimal points

2 years ago

I finished the tree pattern recognising code. Then i realised that I could use the pattern to find other things like patches of grass/concrete pavement/roof tiles. Therefore i could count the percentage area of each of these things inside a given grid. The cropping portion of the code was so I could present the data using a percentage to 2 decimal places (for cleanliness). and there were at least 50000 grids so i couldn't manually crop them all.

the problem with nf() however was that i needed to specify a left hand side AND a right hand side limit to digits, and it would force a percentage like 09.55%, the zero before the nine was simply ugly.

Thanks for feedback

toxmeister

Re: setting decimal points

2 years ago

you can just leave the 1st nf() parameter at 1, e.g. nf(1,2) will not create leading zeros, but truncate to 2 digits after the dot...

You can also use String.format() to achieve the same (and much more), e.g. useful to format multiple values at once:

println(String.format("PI=%.2f or %.4f",PI,PI)); // result: "PI=3.14 or 3.1416"

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