# compile and load the shared object.  From unix type:
# cc -c genfield.c 
# ld -o genfield.so -shared genfield.o -lc -lm
#
# Once in Splus, you need to dynamically load the shared object
# file.  Do this with the following command:
#
# dyn.load.shared("./genfield.so")
# options("object.size"=5e7)


# now simulate some things...

 # coefficients for straw
 #        10     01   1-1  11    20    02  precision

bstraw_c(.595,-.209,.198,.105,-.179,-.011,1.0)

x_matrix(rnorm(100*100),ncol=100,nrow=100)
x_genfield(x,bstraw)
image(x)
best_mple12(straw)
z_genfield(x,best,seed=2)
image(z)

 # coefficients for wool
 #        10     01   1-1  11    20    02  precision

wool_c(.440, .227,-.080,-.042,-.051, .005,1.0)
leather_c(.548, .186,-.068,-.050,-.101,-.019,1.0)
water_c(.51948, .14985,-.06494,-.07592,-.02597,-.00300,0.4995)
wood_c(.43114, .21956,-.10679,-.10379, .06188,-.00200,0.500)

xwool_genfield(matrix(rnorm(100*100),ncol=100,nrow=100),wool)
xleather_genfield(matrix(rnorm(100*100),ncol=100,nrow=100),leather)
xwater_genfield(matrix(rnorm(100*100),ncol=100,nrow=100),water)
xwood_genfield(matrix(rnorm(100*100),ncol=100,nrow=100),wood)

par(mfrow=c(2,3),pty="s",oma=c(0,0,0,0),mar=c(0,0,2,0))
image(x); mtext("straw",side=3,line=1)
image(xwool); mtext("wool",side=3,line=1)
image(xleather); mtext("leather",side=3,line=1)
image(t(xwater)); mtext("water",side=3,line=1)
image(xwood); mtext("wood",side=3,line=1)


# generates a 3rd order Gaussian MRF
# This function calls the C function sgenfield() 
# See the Splus manual for interfacing with C programs.

  genfield  <- function(x,beta,iter=100,seed=1){
       n_dim(x)[1]; m_dim(x)[2]
       lambda_beta[7]
       xv_as.vector(x)
       z_.C("sgenfield",x=as.double(xv),
                         as.integer(n),
                         as.integer(m),
                         as.double(beta),
                         as.double(lambda),
                         as.integer(iter),
                         as.integer(seed))
       x_matrix(z$x,nrow=n)
       return(x)
  }