Mathematical help

[murfitUK]

I am attempting to use php and a pdf creator to generate a chart. It is the mathematical bits I need help with. Basically, the chart has 7 lines (spokes) radiating at equal angles from the centre.

<?php// create the pdfinclude ("class.ezpdf.php");$pdf =& new Cezpdf();$pdf -> selectFont("./fonts/Helvetica.afm"); // these value determine the position and size of the graph// (0,0 is the bottom left hand corner of the page)// x1 is the x centre of the graph$x1 = 200;// y1 is the y centre of the graph$y1 = 200;// s is the scalar$s = 100; // create the skeleton of the graphfor ($spoke=1; $spoke<=7; $spoke++)  {  $angle = ($spoke-1) * (360/7);  $x2 = (sin($angle) * $s) + $x1;  $y2 = (cos($angle) * $s) + $y1;  // draw a line from (x1,y1) to (x2,y2)  $pdf -> line($x1, $y1, $x2, $y2);  } // output the result$pdf -> ezStream();?>

The first spoke works OK but it all goes downhill from there. I have attached the pdf output so you can see what I mean. What makes this worse is that my university degree is in mathematics!!! But it was 30 years ago and I've forgotten everything I ever learned.

graph.pdf

[thescientist]

what's the result you're trying to achieve?

[justsomeguy]

sin and cos expect arguments in radians, not degrees.

[Ingolme]

The sin() and cos() functions use radians. Instead of 360/7 use 2*PI / 7. Also, since this is a value that never changes, calculate it once outside of the loop.

[thescientist]

ah. indeed they dohttp://php.net/manual/en/function.sin.phphttp://php.net/manual/en/function.cos.php

[murfitUK]

I'm so glad it turned out to be a php problem and not that I'd forgotten everything I had ever learned! I didn't realise that sin and cos needed radians and not degrees. Interestingly, my apache server returns PI as 0. I have to use M_PI. Don't know why. The succesful result is attached as graph2. The eventual aim is for my users to be able to generate a chart like that attached as example. At the moment they use excel but want the data stored on their client database instead. I have already got the database set up for them to enter the data and now concentrating on creating the results. Thanks everyone.

graph2.pdf

example.pdf

[thescientist]

Interestingly, my apache server returns PI as 0. I have to use M_PI. Don't know why. The succesful result is attached as graph2.

That's not Apache, that's PHP. http://php.net/manual/en/math.constants.php PHP has support for predefined constants, and some specifically for Math, which is where the M_ comes from, presumably in attempt to namespace these constants.