On Aug 26, 10:55*am, serave <ramirez.sebast...@gmail.comwrote:

On 26 ago, 01:53, cwdjrxyz <spamtr...@cwdjr.infowrote:

On Aug 25, 9:18*pm, serave <ramirez.sebast...@gmail.comwrote:

Hi i'm new in this group. I need some help with php. I need to draw

any mathematical function i get through a form?

Do you mean you need to draw a curve from the results of solving an

exact equation or do you mean you need to fit the best curve to a set

of experimental measured points that always have some error. In the

second case, a good bit of statistical calculation often is required.

If you are a glutton for punishment, you can do this with the Math

functions of Javascript or php. You would be much better off using a

language such as c++ or even old Fortran which are better designed for

math and science calculations and curve fitting. There are all sorts

of math programs for curve fitting, plotting, solving equations, etc

and these are what most people now use when working with math. You

will find such programs advertised in many scientific and math

journals. Unfortunately many of these programs are rather expensive

for an individual, but they very soon pay for themselves in time saved

for a company that needs many such math and curve fitting programs and

has to hire many highly trained people with advanced degrees.

I have 2 examples of drawing curves from solution of math equations

at:http://www.cwdjr.net/math/bessel_function2.html

http://www.cwdjr.net/geometricDraw/curve_write.html

This was done using the math functions of Javascript, but the Math

functions of php could have been used. These pages are very old, and I

likely would use different code if doing them today. Now if you wanted

to input experimental points and curve fit to the data, the

calculations become much more complicated because of the statistical

calculations needed to give the curve that best fits the experimental

data. You would input the experimental data into arrays most likely.

No i just need to draw the function, no need to draw the best

aproximation. Is just drawing the curve based on a mathematical

equation like y=e^(x-5)+sin(5x^3)-45x^(2/3) or something like that

Then you solve the equation for say y at closely spaced points of x

using the Math functions of Javascript or php at closely spaced points

of the x coordinate and display each point calculated using a

document.write in Javascript. The structure of code is much the same

in php, but the details are rather different.

In the first example I gave you, the Bessel function of the type given

has no exact solution involving simple math functions. It must be

solved in terms of infinite series, and this is quite tricky and

requires a very good understanding of math that usually is taught at

the college level in courses such as advanced calculus.

The second example I gave you with several curves is much more simple,

as the equation can be solved in terms of known simple functions.

Considering the calculation of the 2 circles, the equations are solved

using JavaScript math and points are written using document.write.

That part of the code is:

var c1=.02,c3=.01 // angle

increment

var px1=270 // center x

var py1=180 // center y

var r1=165,r2=175,r3=160,r4=185 // radius

var ns1=325,ns3=650 // number of steps

var z=0,y,x ;

for (i=0;i < ns1;++i) {

x = (px1 + r1*Math.cos(z)); y= (py1 + r1*Math.sin(z));

document.write('<div style=\"position:absolute; left:'+x+'px; top:'+y

+'px; height:4px; width:4px; background-color: #ff0000; z-index:1;

color:#ff0001; font-size:1px\">'+sym+'<\/div>');

z = z + c1;

}

var z2=0,y2,x2 ;

for (i=0;i < ns1;++i) {

x2 = (px1 + r2*Math.cos(z2)); y2= (py1 + r2*Math.sin(z2));

document.write('<div style=\"position:absolute; left:'+x2+'px;

top:'+y2+'px; height:4px; width:4px; background-color: #00ff00; z-

index:1; color:#00ff01; font-size:1px\">'+sym+'<\/div>');

z2 = z2 + c1;

}

It turns out that the equations for the 2 circles are best solved in

terms of polar coordinates, and you loop over many points. You must

keep in mind that the origin of the display is taken at the upper left

corner of the monitor. The positive x direction points to the right as

usual, but the positive y direction points down in contrast to

pointing upward as usually used in math texts. This is just how

JavaScript math functions were set up - don't blame me for that :-).

Thus the key is a fair general knowledge of JavaScript or php, and a

good knowledge of their math functions as well as a knowledge of how

to solve mathematical equations in which you are interested. Every

equation is somewhat different. Thus it is easy to appreciate why

special programs are sold for solving math equations and plotting

results.For calculations that are very time consuming, fewer exact

points often are calculated and some type of extrapolation is used to

calculate points between the exact points.