Math equation parser/plotter

[Felipe Barone]

I know some of you guys are working on this too, but here it is my
first sample for plotting equation using google chart API:

http://www.felipebarone.com/plot-function-google.php

this is a first draft and im using PHP to get the values and parsing
into a valid GC url. For now it only takes simple functions (no
trigonometrics, for example) and only one function at a time. Also im
using text encoding data (http://code.google.com/apis/chart/#text) so
if the range is too wide, it gets over 100 points and chart is
plotted....

anyways, this is a draft as i said and any comments suggestions are
very welcome! if anyone out there playing with PHP and CG let me know
so we can exchange experiences and codes!

best regards,

Felipe

[Uwe Maurer]

Hi Felipe,

thanks for doing this! It is very useful.
I have some suggestions:
- In the text encoding, instead of
13.3333333333,12.9363333333,12.5453333333,12.1603333333,11.7813333333,11.4083333333,
you can use
13.3,12.9,12.5,12.1,11.7,11.4
This makes the URL much shorter and the chart image stays the same.

- For the labels you can use the chxr parameter (it does the labels
automatically then).
I think in your current version is a bug when the x range is eg -1
to 1, it gives -1, 1, 1 as labels, instead of -1, 0, 1
- Also if the space between the x values is always the same, it is
better to use cht=lc instead of cht=lxy. Then you don't need to
specify the x values.

Thanks,
Uwe

[Felipe Barone]

Hi Uwe,

thanks for replying! Thanks for the sugestion on the encoding, will
do it as soon as i get home! Im vacation in Bahia (Brazil) right now!

I see the axis issue and indeed they need some work. I let you know
when i get a new version of it.

Best regards,

Felipe

On Jan 7, 6:03 am, Uwe Maurer <uwe.mau...@google.com> wrote:
> Hi Felipe,
>
> thanks for doing this! It is very useful.
> I have some suggestions:
> - In the text encoding, instead of

> 13.3333333333,12.9363333333,12.5453333333,12.1603333333,11.7813333333,11.40­83333333,

> > Felipe- Hide quoted text -
>
> - Show quoted text -

[Felipe Barone]

Greetings Uwe,

i have made some changes on the script fixing:
1 - Rounded the values to get a shorter URL.
2 - Labels for axis are fixed.
3 - For some simple functions, the roots (e.g. F(x) = 0) are marked
with a red circle.

I plan to implement some other functionalities like max and minimum
for a functions and eventually, more than one function in same
chart....

I still have an issue with points outside the chart range that
sometimes totally screw the chart, for example try:
fx: x*x*x+3*x*x-3
-4 >= x >= 3
-2 >= x >= 2

I have a couple ideas to fix this, but any suggestions are very
welcome. I still didn't get to implement your suggestion to use
cht=lc instead of cht=lxy, which indeed will make URL even shorter.

regards,

Felipe

[Uwe Maurer]

Hi Felipe,

very nice updates! I added the link to your function plotter to the
links page.

Thanks,
Uwe