{
#	Logistic Regression
#Problem 15-1 of Helsel book..

	test=matrix(scan("prob-15-1.txt"), ncol=5, byrow=T)
	y = test[,5]
	x = test[,1:4]

	N = length(y)

#Fit a logistic model to all the variables..	
	logcalib=glm(y ~ x,family="binomial")
#estimate the value at the data points
	logpred=predict.glm(logcalib,data.frame(x=x),se.fit=T,type="response")
	plot(y,logpred$fit,xlab="Actual",ylab="Estimated",cex=1.5)

# provide the ANOVA table
#	summary(logcalib)


#commands for x-validated estimates..

#	PART - II X-validated estimates..

		yxval=1:N
		positions = 1:N
        	for( ypos in 1:N){
		
			positions1=positions[positions!=ypos]
			positions2=positions[positions==ypos]

			yy=y[positions1]
			xx=x[positions1,]
			xxpred=x[positions2,]

			logcalib=glm(yy~xx,family="binomial")
			xx[1,]=xxpred
		        logpred=predict.glm(logcalib,data.frame(xx=xx),se.fit=T,type="response")
			yxval[ypos]=logpred$fit[1]
			}	#Loop ends for each cross validated year

	plot(y,yxval,xlab="Actual",ylab="Estimated",cex=1.5)
	
	}	#End of the Program