#include<stdio.h>
#include<stdlib.h>
#include<math.h>
#include<curses.h>
#define MAX 100


int n,i,j, N, which,count;
float x[100], y[100], X, X2, Y, XY, a,b,sum,dev;
char input[10], output[10];
FILE *fptr;
int main(){

   initscr();
echo();
resize_term(40,80);
    if(!has_colors()){
	endwin();
	exit(0);
    }
    if(start_color() != OK){
	endwin();
	exit(0);
    }
    init_pair(1, COLOR_RED, COLOR_BLACK);
    init_pair(2, COLOR_YELLOW, COLOR_BLACK);
    init_pair(3, COLOR_BLUE, COLOR_BLACK);
    init_pair(0, COLOR_WHITE, COLOR_BLACK);
    init_pair(4, COLOR_BLACK, COLOR_YELLOW);
    init_pair(5, COLOR_CYAN, COLOR_BLACK);

    move(1, 10);
    attron(A_UNDERLINE);
    printw("Regression analysis");
    attroff(A_UNDERLINE);
    move(3, 1);
    printw("Interactive mode (i) or read from file (f)? ");  
    attrset(COLOR_PAIR(2));
    getstr(input);
    attrset(COLOR_PAIR(0));
    which=-1;
    if(strcmp(input,"i")==0 || strcmp(input,"I")==0)
	which=0;
    if(strcmp(input,"f")==0 || strcmp(input,"F")==0)
	which=1;  
    if(which==-1){
	move(5,1);
	printw("Don't prompt OR read from file, bye-bye!");
	refresh();
	endwin();
	exit(0);
    }
    if(which==0){
	move(5,1);
	printw("How many (x,y) pairs do you want to enter? ");
	attrset(COLOR_PAIR(2));
	getstr(input);
	attrset(COLOR_PAIR(0));
	N=atoi(input);
	if(N<0 || N>100){
	    move(7,1);
	    printw("Sorry, thats out of range");
	    refresh();
	    endwin();
	    exit(0);
	}
	count=0;
	for(i=0;i<=N/2;i++){
	    
	    for(j=0;j<2;j++){
		if(count <= N-1){
		move(9+2*i, 28*j);
		printw("x[%d]= ", count+1);
		attrset(COLOR_PAIR(1));
		getstr(input);
		attrset(COLOR_PAIR(0));
		x[count]=atof(input);
		 move(9+2*i, 28*j+14); 
		printw("y[%d]= ", count+1);
		attrset(COLOR_PAIR(1));
		getstr(input);
		attrset(COLOR_PAIR(0));
		y[count]=atof(input);
		count=count+1;}
	    }
	}
	
	N=count;

	move(11+2*N/2, 1);
	X=0.0;
	Y=0.0;
	X2=0.0;
	XY=0.0;
	for(i=0;i<N;i++){
	    X=X+x[i];
	    Y=Y+y[i];
	    X2=X2+x[i]*x[i];
	    XY=XY+x[i]*y[i];
	}
	a=((float)N*XY-X*Y)/((float)N*X2-X*X);
	b=-(XY*X-X2*Y)/((float)N*X2-X*X);

	printw("Slope a = ");
	attrset(COLOR_PAIR(5));
	printw(" %f", a);
	attrset(COLOR_PAIR(0));
	dev=0.0;
	for(i=0;i<N;i++){
	    dev=dev+(x[i]-sum)*(x[i]-sum);}
	dev=sqrt(dev/(float)(N-1));
	move(11+2*N/2, 25);
	printw("Intercept b =");
	attrset(COLOR_PAIR(5));
	printw(" %f", b);
	attrset(COLOR_PAIR(0));
    refresh();




    } /* interactive mode */


if(which==1){
	move(5,1);
	printw("What is the name of the data file? ");
	attrset(COLOR_PAIR(2));
	getstr(input);
	attrset(COLOR_PAIR(0));
	fptr=fopen(input,"r");
	if(fptr !=NULL){
	i=0;
	while(fscanf(fptr,"%f%f",&x[i], &y[i]) != EOF){
	    i=i+1;
	}
	N=i;
	if(N<0 || N>100){
	    move(7,1);
	    printw("Sorry, too many data points");
	    refresh();
	    endwin();
	    exit(0);
	}
	count=0;
	for(i=0;i<=N/2;i++){
	    
	    for(j=0;j<2;j++){
		if(count <= N-1){
		move(9+2*i, 30*j);
		printw("(x[%d],y[%d])= ", count+1,count+1);
		attrset(COLOR_PAIR(1));
		printw("(%4.3f, %4.3f)", x[count],y[count]);
		attrset(COLOR_PAIR(0));
		count=count+1;}
	    }
	}


N=count;

	move(11+2*N/2, 1);
	X=0.0;
	Y=0.0;
	X2=0.0;
	XY=0.0;
	for(i=0;i<N;i++){
	    X=X+x[i];
	    Y=Y+y[i];
	    X2=X2+x[i]*x[i];
	    XY=XY+x[i]*y[i];
	}
	a=((float)N*XY-X*Y)/((float)N*X2-X*X);
	b=-(XY*X-X2*Y)/((float)N*X2-X*X);

	printw("Slope a = ");
	attrset(COLOR_PAIR(5));
	printw(" %f", a);
	attrset(COLOR_PAIR(0));
	dev=0.0;
	for(i=0;i<N;i++){
	    dev=dev+(x[i]-sum)*(x[i]-sum);}
	dev=sqrt(dev/(float)(N-1));
	move(11+2*N/2, 25);
	printw("Intercept b =");
	attrset(COLOR_PAIR(5));
	printw(" %f", b);
	attrset(COLOR_PAIR(0));
    refresh();
    fclose(fptr);}
	else{
	    move(11,1);
	    printw("There is no such file in the working directory");
	    refresh();
	    endwin();
	    exit(0);
	}



    } /* file mode */




 
move(13+N,1);
printw("Type anything <RET> to quit ");
attrset(COLOR_PAIR(1));
getstr(input);
    endwin();
    exit(0);

}