FLEGENDRE

       Compute the first M terms in a Legendre polynomial expansion.

       Meant to be used as a supplied function to SVDFIT.
       This procedure became partially obsolete in IDL V5.0 with the
       introduction of the /LEGENDRE keyword to SVDFIT and the associated
       SVDLEG function.    However, note that, unlike SVDLEG, FLEGENDRE works
       on vector values of X.

       result = FLEGENDRE( X, M)

       X - the value of the independent variable, scalar or vector
       M - number of term of the Legendre expansion to compute, integer scalar

       result - (N,M) array, where N is the number of elements in X and M
               is the order.   Contains the value of each Legendre term for
               each value of X

       (1) If x = 2.88 and M = 3 then
       IDL> print, flegendre(x,3)   ==>   [1.00, 2.88, 11.9416]
       This result can be checked by explicitly computing the first 3 Legendre
       terms, 1.0, x, 0.5*( 3*x^2 -1)
       (2) Find the coefficients to an M term Legendre polynomial that gives
               the best least-squares fit to a dataset (x,y)
               IDL> coeff = SVDFIT( x,y,M,func='flegendre')
           The coefficients can then be supplied to the function POLYLEG to
               compute the best YFIT values for any X.

       The recurrence relation for the Legendre polynomials is used to compute
       each term.   Compare with the function FLEG in "Numerical Recipes"
       by Press et al. (1992), p. 674

       Written     Wayne Landsman    Hughes STX      April 1995
       Converted to IDL V5.0   W. Landsman   September 1997

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