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What is it?

Its a web page which will draw graphs.


Can I use it?

It uses HTML5, so it needs a fairly modern browser. In Windows XP, Internet Explorer does not work (so don't use it). Firefox (26) works.
On Ubuntu 12.04, it works on Chrome, Firefox and Opera.
Let me know what else it works on.
It uses a screen width or 1280 by 948, so if your screen is smaller than that, you'll have to scroll around.


Where is it?

>>>>>>>>>>>>>>>>>>>> It's here <<<<<<<<<<<<<<<<<<<<<<


New in version 1.1

Up to 10 functions are displayed in a table and can be edited there. Click Replot to see changes. User defined functions can now be saved, and are reloaded whne teh page is re-visited. Functions defined as a series of terms can be plotted.

How do you use it?

You start seeing x and y axes, and controls on the right. As the mouse moves over the graph, the (x,y) andspark (r, θ) co-ordinates are displayed. The left right etc buttons alter the axes limits.

Plot an expression

You can input an expression and the graph will be drawn, with x as the independent variable. Use * for multiplication. So maths 2(x+3) is here 2*(x+3). You can select the color, then click 'Re-plot now' to plot it. Close ends the dialog but leaves it still displayed. Hide closes and hides the expression. You can use built-in functions, functions you define, and parameters, as described below.

Built-in functions

The following are built-in: sin, abs, acos, atan, ceil, exp, floor, log, pow, sqrt, tan and cos.
Used like sin(2*x+3).

Parameters

Lower-case single letters a to z can be used as parameters. In other words you can plot something like m*x+c, or sin(a*x). These are initially 1, except e, which is e. pi is π. In the 'Vary parameters' dialog, you can assign a new value to a parameter, or use the slider to vary it and see the graphs change.

New function

You can define your own functions. Enter a function name (like f) and an expression for it (like x+1). Choose a color for the graph. If you check 'Plot this function' it will be graphed - otherwise not. The idea is you might define a function but just use it in other functions, and you don't want to clutter the display. Edit function allows you to edit these values.

Family of Curves

band This lets you draw a set of related functions, like m*x+c as m is changed.

Parametric curves

This lets you display curves defined parametrically - in other words, x and y are given as functions of a parameter 't'.

Polar co-ordinates

For curves defined using polar co-ordinates ie r=f(θ). Use t for θ

Series

This plots a function defined as the sum of a series of terms. As an example, the default plots the sum of sin(nx)/n, which is an approximation to the Fourier series of a sawtooth wave.

First order differential equations

Of the form dy/dx = f(x,y)
van de graph generator - geddit?

Bug reports and comments

To wm at waltermilner.com please.


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