Legendre polynomials plot help

Hi,

I need to plot the first 5 legendre polynomials. I have managed to get the expressions by writing a code for it.

>>syms x b

for n = 1:5

      a(n) = 1./((2.^(n-1)).*factorial(n-1));
      b = ((x*x)-1).^(n-1);
      c = diff(b,n-1);
      P_n = a(n).*c
  end

But now I can't figure out how to write a code to calculate its value for x varying from -1 to 1 with an increment of 0.1.

Any ideas would be highly appreciated.

Thanks

Ushnik

Answer 1

[Walter Roberson]

Change

P_n = a(n).*c

to

P(n) = a(n).*c;

Now for any given n,

xvals = -1 : 0.1 : 1;
pvals = double(subs(P(n), x, xvals));

[Ushnik Mukherjee]

Hi Walter,

I got to thinking, and I tried out this:

xvals = -1:0.1:1;

pvals1 = double(subs(P(1), x, xvals));

pvals2 = double(subs(P(2), x, xvals));

pvals3 = double(subs(P(3), x, xvals));

pvals4 = double(subs(P(4), x, xvals));

pvals5 = double(subs(P(5), x, xvals));

I have checked the answers and it looks perfect.

Thanks a ton!

Cheers

Ushnik