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From |
Glenn Goldsmith <glenn.goldsmith@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
RE: Re: st: passing optional arguments to functions in Mata |

Date |
Tue, 16 Jun 2009 22:28:20 +0100 |

Hi Nathan, Stas' solution is good for the specific example you gave (passing exactly one argument). More generally, if you want to be able to pass a variable number of arguments to the inner function, something like the code below may be useful (omitted code identical to the original except where indicated): **************************************************************** scalar NDint( pointer(real scalar function) scalar f, real scalar lower, real scalar higher, real scalar m, | z1, z2, z3, z4, z5, z6, z7) { ... for (i=1; i<=n; i++) { x = lower + ((i-1)*width) if (args()==4) Y[i,1] = (*f)(x) if (args()==5) Y[i,1] = (*f)(x,z1) if (args()==6) Y[i,1] = (*f)(x,z1, z2) if (args()==7) Y[i,1] = (*f)(x,z1, z2, z3) if (args()==8) Y[i,1] = (*f)(x,z1, z2, z3, z4) if (args()==9) Y[i,1] = (*f)(x,z1, z2, z3, z4, z5) if (args()==10) Y[i,1] = (*f)(x,z1, z2, z3, z4, z5, z6) if (args()==11) Y[i,1] = (*f)(x,z1, z2, z3, z4, z5, z6, z7) } ... } ********************************************************************* HTH, Glenn. Stas Kolenikov <skolenik@gmail.com> wrote: Shouldn't just (*f)(x,z) work? Of course z needs to be defined in NDint(). A weaker option is to use -external- declarations. That makes the code messy and occasion-specific, which given your style you probably won't like :)) On 6/16/09, Nathan Danneman <ndanneman@gmail.com> wrote: > Hi all, > > I have written a function for a part of a larger program. This > program generates a numeric integral for a function that it calls. I > would like to allow the outter function to pass several optional > arguments (between zero and seven) on to the called function which is > being integrated, which could then pass those arguments on to another > lower-level function...etc. The code for the integration function is > below. In the pasted example, I integrate the function named "trial" > at bottom. As a very simple example, how could I get the overall > function, NDint, to pass the z parameter on to "trial"? > > Thanks, > Nathan > > > //An n-slice integration routine using simpson's approximation > > mata > mata clear > mata set matalnum off > > scalar NDint( > // to perform integration via simpson'sapproximation > pointer(real scalar function) scalar f, > //points to the functionto be integrated > real scalar lower, > //lower bound of integration > real scalar higher, > //upper bound > real scalar m) // where m = number of slices, must be an EVEN number > { > > if ( (m/2) != (floor(m/2)) ) _error("m must be an EVEN number") > > real scalar width //I like declarations, your mileage may vary > real colvector Y > real rowvector X > real scalar n //slices plus one > > n = m+1 > > if (lower > higher) _error("limits of integration reversed") > //make sure upper > lower NB: better to use _error() than > return() > > width = (higher-lower) / m > //calculates width of each "slice" > > Y = J(n,1,.) > //creates an empty 15 x 1 column vector > for (i=1; i<=n; i++) { > x = lower + ((i-1)*width) > Y[i,1] = (*f)(x) > //places function evaluations directly into Y, > avoiding all the copying you were doing previously > } > > X = J(1,n,.) > for (i=1;i<=n; i++) { > if (i==1) X[1,i] = 1 > if (i==n) X[1,i] = 1 > if ((i/2) == (floor(i/2))) X[1,i] = 4 > if ( ((i+1)/2) == (floor( ((i+1)/2)) ) & (i!=1) & (i!=n) ) X[1,i] = 2 > } > > > return(X*Y*width/3) //matrix multiplication makes this quicker > and more readable > > } > > scalar trial(real scalar x) { > //declares the output to be a scalar. otherwise > you could run into problems in the main program > return(z*exp(x)) > } > > f = &trial() > > NDint(f, 0, 4, 60) > > end > > > > -- > "Imagination is more important than knowledge..." > -- Albert Einstein > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > -- Stas Kolenikov, also found at http://stas.kolenikov.name Small print: I use this email account for mailing lists * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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