Lindo Systems

! Graphing of Univariate functions in LINGO,
  Normal distribution vs. Student t (ChartPdfNormVsStudT);
! Keywords: @CHARTPCURVE, Chart, @FORMAT, Function, Graph, LINGO, 
     Normal curve, Procedure, Student t distribution, Univariate;
PROCEDURE PDFcompute:
  y1 = @PNORMPDF( 0, sigma, x);
  y2 = @PSTUTPDF( df, x);
ENDPROCEDURE
calc:  
   sigma = 1.2; ! Standard deviation for the Normal distribution;
   df = 2;      ! Degrees of freedom for the Student t distribution;
   LB = -5;     ! Lower bound for x;
   UB =  5;     ! Upper bound for x;
   @CHARTPCURVE( 
    'Sample PDF Curve Chart', ! Chart title;
    'x',         ! Title for X axis;
    'Frequency', ! Title for Y axis;
    PDFcompute,  ! Name of function procedure;
    x, LB, UB,   ! X variable, LB and UB;
    ! Title for curves, output variables;
    'y = Normal( 0,     '+@format(sigma,'3.1f')+')', y1,
    'y = Student t, df= '+@format(df,'3.1f'),    y2);
 endcalc