how to make a dynamic function integral Graph from user input

[vengg...@gmail.com]

i have a problem to make a dynamic graph from this library http://jsxgraph.uni-bayreuth.de/docs/symbols/Integral.html

i have made a dynamic x1 and x2 from user input and it is success (oh yeahhhh!!!) 

var c1 = board.create('functiongraph', [function (t) { return t*t*t; }]);
var i1 = board.create('integral', [[x1,x2], c1]);

but, how can i make function(t) depends from user input ?

 for example user input x^2+4x from texboxt and the code will generate this: 

var fx = $("#fx").val(); // fx = x^2 + 4x

var c1 = board.create('functiongraph', [function (x) { return fx; }]); 

i have tried this but it doesn`t draw anything ? any solutions ?

[Murray Bourne]

Hi Venggeance

You need to use an "eval" as per this example:

http://jsxgraph.uni-bayreuth.de/wiki/index.php/Change_Equation_of_a_Graph

I've been trying to do it without the evils of eval, but haven't figured out how, yet.

Regards,
Murray Bourne
                                                                        
Interactive Mathematics: http://www.intmath.com/

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[calvin sugianto]

hi Murray, it works , thanks bro

but now the problem is when i input x^2 or 3x or cos(x) , it doesn`t work, do you have any idea to generate it to becomes x*x , 3*x , Math.cos(x) ?

and the image of cursor {+,-, <- , -> } doesn`t appear, what`s the problem anyway?

Best Regards,

Calvin

[calvin sugianto]

i have solved the 3x, 2x , 9x,etc problems

with this code:

fx2 = fx.replace(/(\d)\s*x/g,"$1 * x");

 

[Alfred Wassermann]

Depending on the application, the use of eval() may not be the most secure way to convert a function term into a JavaScript function. JSXGraph comes with its own parser JessieCode (see https://github.com/jsxgraph/JessieCode). JessieCode reads Math synatx, i.e. x^2 is converted to x*x, …

Here is your example realized with JessieCode:

    var fx = $("#fx"

).val();
    var f = board.jc.snippet(fx, true, 'x', true);
    var c1 = board.create('functiongraph', [f]);

Best wishes,
Alfred

​

[calvin sugianto]

oh Yeahhhh, it works bro, Thx a lot Alfred

but based on this tutorial http://jsxgraph.uni-bayreuth.de/wiki/index.php/Change_Equation_of_a_Graph

how to make the button image {+,-, <- , -> } appear?

because in my web, the symbol change into the weird symbol 

[Alfred Wassermann]

This is probably an encoding problem. If possible, try enforcing UTF-8 encoding on your websites:

<meta http-equiv="content-type" content="text/html;charset=utf-8">

Best wishes,
Alfred

​

[calvin sugianto]

thank you very much Alfred, it works, but what is encoding mean and it`s functionality

[Alfred Wassermann]

UTF-8 is the the name of the encoding system how text is converted into bits.
See http://en.wikipedia.org/wiki/UTF-8

Best wishes,
Alfred