Re: How to draw a line graph using javascript
- From: Dr John Stockton <jrs@xxxxxxxxxxxxxxxxxx>
- Date: Wed, 26 Oct 2005 14:23:13 +0100
JRS: In article <6didnYn9zb2excPeRVn-jQ@xxxxxxxxxxx>, dated Tue, 25 Oct
2005 12:06:44, seen in news:comp.lang.javascript, Randy Webb
<HikksNotAtHome@xxxxxxx> posted :
>srinivas said the following on 10/25/2005 11:04 AM:
>> I have one requirement.
>
>And it is an impossible requirement.
>
>> Is there any way to create a line graph using javascript.
>> But the thing is it should work in all browsers.
>
>That "thing" is what makes your requirement impossible.
Well, it's pretty difficult to see how it could be done in Lynx, unless
Ascii-art is adequate, in which case any browser that can handle script
should do.
How many images can one put on a single page, if the images themselves
are simple?
In graphics\, fig-dot.gif (if I remember to upload it; otherwise use
fig-_) and fig-0.gif are here images of dot and 0, but pretend they are
white and black bricks and smaller. Then the following javascript code,
tested in my js-quick.htm, generated a very crude diagram of a black-
filled parabola.
for (y=-6;y<7;y++) {
for (x=-2;x<15;x++) { Z = ["dot", "0"][+(2*x>y*y)]
document.writeln("<img src='graphics/fig-", Z, ".gif'>") }
document.writeln("<br>") }
On a more recent machine, presumably more images can be used at
reasonable speed.
Also, if you prepare a set of 64 square GIFs, one for each combination
of the 8 principal spokes being present or absent, you can generate a
line drawing by computing which to write in a grid.
If they are transparent GIFs, then I think you can absolutely position
them on top of each other, and stretch/squash them to get lines at
computed angles. The axes, of course, would be prepared as a single
GIF, if of constant scale.
You'd prepare your data as a list or array, of course, and run through
it computing the output of each element.
If you can use only more recent browsers, you should probably use DOM
methods to construct the relevant part of the page.
Note also that HTML can display a BMP file, and AIUI the BMP format is
simple. You could use an application to compute a BMP, by adding your
overlay to your template, and display that.
--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 MIME. ©
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