bccomp

Client Joined: Oct 07, 2003 Posts: 735 Location: Ohio

php.net states that bccomp — compare two arbitrary precision numbers.

Code:

int bccomp  ( string $left_operand  , string $right_operand  [, int $scale  ] )

Returns 0 if the two operands are equal, 1 if the left_operand is larger than the right_operand , -1 otherwise.

Code:

if (bccomp($x, '0') == -1)

if I took out the bccomp I wouldn't need == -1 either.

Then if ($x < '0') then I could do something else like reduce $r by 0.1

So I could recode this to say

Code:

if ($x < 0) {


      $r = ($r - 0.1);


      }

I have a function using bcmath which I have been unable to get running on my Mac o sx server at work. I need to recode all this an use normal math.

Code:

function get_base($x){


   //divide by 10 and multiply by 10, so that


   //we can get rid of the digit at the 0.0x position.


   $r = bcdiv($x, '10');


   $r = bcmul($r, '10');


   //if the number is less than 0, reduce it by 0.1


   if (bccomp($x, '0') == -1)


      $r = bcsub($r, '0.1');





   return $r;


}

registered · Posted: Thu Feb 26, 2009 7:28 pm

I don't understand necessarily why it is doing precision functions. If all this function is doing is removing the hundreds digit and such, you could easily just use number_format

Quote:

return number_format($x, 1);

http://us.php.net/manual/en/function.number-format.php

Posted: Thu Feb 26, 2009 7:51 pm

The values are called discriminators and could be anywhere from -.9 to .9

I will have around 100 of them for each exam (100 questions)

I am trying to group them into ranges.

This query

Code:




$chart = $db->sql_query("SELECT `discri`, COUNT(`discri`) AS `occurrence` FROM question_stats WHERE quiz_id = '$qid' GROUP BY `discri` ORDER BY `discri`");


$occurrence = array();


$descri = array();


while( $row = $db->sql_fetchrow($chart)) {


    $occurrence[] = $row['occurrence'];


    $descri[] = $row['discri'];

gave me these arrays.

Code:

Array


(


[0] => 1


[1] => 1


[2] => 1


[3] => 4


[4] => 1


[5] => 1


[6] => 1


[7] => 2


[8] => 1


[9] => 4


[10] => 1


[11] => 2


[12] => 4


[13] => 1


[14] => 4


[15] => 3


[16] => 4


[17] => 4


[18] => 1


[19] => 4


[20] => 3


[21] => 1


[22] => 3


[23] => 6


[24] => 1


[25] => 4


[26] => 2


[27] => 1


[28] => 5


[29] => 2


[30] => 2


[31] => 4


[32] => 1


[33] => 1


[34] => 2


[35] => 1


[36] => 1


[37] => 2


[38] => 1


[39] => 1


[40] => 1


)





Array


(


[0] => -0.09


[1] => -0.06


[2] => -0.03


[3] => 0.00


[4] => 0.02


[5] => 0.03


[6] => 0.05


[7] => 0.09


[8] => 0.10


[9] => 0.11


[10] => 0.12


[11] => 0.13


[12] => 0.14


[13] => 0.16


[14] => 0.18


[15] => 0.19


[16] => 0.20


[17] => 0.21


[18] => 0.22


[19] => 0.23


[20] => 0.24


[21] => 0.25


[22] => 0.26


[23] => 0.27


[24] => 0.28


[25] => 0.29


[26] => 0.30


[27] => 0.31


[28] => 0.32


[29] => 0.33


[30] => 0.34


[31] => 0.35


[32] => 0.36


[33] => 0.38


[34] => 0.40


[35] => 0.41


[36] => 0.42


[37] => 0.44


[38] => 0.46


[39] => 0.49


[40] => 0.50


)

I need to find the minimum value to start my graph and start the first range.

Ranges would look like

Quote:

-0.11 to -0.20
-0.01 to -0.10
0.00 to 0.09
0.10 to 0.19
0.20 to 0.29
0.30 to 0.39

A guy did this for me awhile ago and he used bcmath. I don't exactly know why he used precision functions either.

Involved Joined: Jul 03, 2006 Posts: 273

if you need the minimum value why not just use asort?

registered · New Member Joined: Jan 22, 2009 Posts: 2

bcmath is used to do precise math operations.
it uses string representation of numbers and scale is the number of digits to the right of period.

remember, float is just an approximate so it can't be relied upon.