function lens(){
	if (document.lenscalc.radio1[0].checked){
		quarter();
	}
	else if (document.lenscalc.radio1[1].checked){
		third();
	}
	else if (document.lenscalc.radio1[2].checked){
		half();
	}
	else if (document.lenscalc.radio1[3].checked){
		twothirds();
	}
	else if (document.lenscalc.radio1[4].checked){
		one();
	} else {
	}
}//end function

//1/4 inch
function quarter(){
	var distance = document.lenscalc.distance.value;
	var horizontal = document.lenscalc.horizontal.value;
	var lens_size = document.lenscalc.lens_size.value;
	var vertical = document.lenscalc.vertical.value;
	
	if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
		lens_size = distance/horizontal*3.2;
		vertical = horizontal*.75;
		document.lenscalc.lens_size.value = lens_size;
		document.lenscalc.vertical.value = vertical;
  	} else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
		horizontal = distance/lens_size*3.2;
		vertical = horizontal*.75;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
		distance = horizontal/3.2*lens_size;
		vertical = horizontal*.75;
		document.lenscalc.distance.value = distance;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
		distance = vertical/2.4*lens_size;
		horizontal = vertical/3*4;
		document.lenscalc.distance.value = distance;
		document.lenscalc.horizontal.value = horizontal;
	} else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
		horizontal = vertical/3*4;
		lens_size = distance/horizontal*3.2;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.lens_size.value = lens_size;
	} else {
		alert("One or more of your answers were invalid. Please be sure to enter information in only 2 of the 4 fields.");
	}
}//end function

//1/3 inch
function third(){
	var distance = document.lenscalc.distance.value;
	var horizontal = document.lenscalc.horizontal.value;
	var lens_size = document.lenscalc.lens_size.value;
	var vertical = document.lenscalc.vertical.value;
	
	if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
		lens_size = distance/horizontal*4.4;
		vertical = horizontal*.75;
		document.lenscalc.lens_size.value = lens_size;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
		horizontal = distance/lens_size*4.4;
		vertical = horizontal*.75;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
		distance = horizontal/4.4*lens_size;
		vertical = horizontal*.75;
		document.lenscalc.distance.value = distance;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
		distance = vertical/3.3*lens_size;
		horizontal = vertical/3*4;
		document.lenscalc.distance.value = distance;
		document.lenscalc.horizontal.value = horizontal;
	} else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
		horizontal = vertical/3*4;
		lens_size = distance/horizontal*4.4;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.lens_size.value = lens_size;
	} else {
		alert("One or more of your answers were invalid. Please be sure to enter information in only 2 of the 4 fields.");
	}
}//end function


//1/2 inch
function half(){
	var distance = document.lenscalc.distance.value;
	var horizontal = document.lenscalc.horizontal.value;
	var lens_size = document.lenscalc.lens_size.value;
	var vertical = document.lenscalc.vertical.value;
	
	if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
		lens_size = distance/horizontal*6.4;
		vertical = horizontal*.75;
		document.lenscalc.lens_size.value = lens_size;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
		horizontal = distance/lens_size*6.4;
		vertical = horizontal*.75;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
		distance = horizontal/6.4*lens_size;
		vertical = horizontal*.75;
		document.lenscalc.distance.value = distance;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
		distance = vertical/4.8*lens_size;
		horizontal = vertical/3*4;
		document.lenscalc.distance.value = distance;
		document.lenscalc.horizontal.value = horizontal;
	} else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
		horizontal = vertical/3*4;
		lens_size = distance/horizontal*6.4;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.lens_size.value = lens_size;
	} else {
		alert("One or more of your answers were invalid. Please be sure to enter information in only 2 of the 4 fields.");
	}
}//end function

//2/3
function twothirds(){
	var distance = document.lenscalc.distance.value;
	var horizontal = document.lenscalc.horizontal.value;
	var lens_size = document.lenscalc.lens_size.value;
	var vertical = document.lenscalc.vertical.value;
	
	if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
		lens_size = distance/horizontal*8.8;
		vertical = horizontal*.75;
		document.lenscalc.lens_size.value = lens_size;
		document.lenscalc.vertical.value = vertical;
	}
	
	else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
		horizontal = distance/lens_size*8.8;
		vertical = horizontal*.75;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.vertical.value = vertical;
	}
	
	else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
		distance = horizontal/8.8*lens_size;
		vertical = horizontal*.75;
		document.lenscalc.distance.value = distance;
		document.lenscalc.vertical.value = vertical;
	}
	
	else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
		distance = vertical/6.6*lens_size;
		horizontal = vertical/3*4;
		document.lenscalc.distance.value = distance;
		document.lenscalc.horizontal.value = horizontal;
	}
	
	else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
		horizontal = vertical/3*4;
		lens_size = distance/horizontal*8.8;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.lens_size.value = lens_size;
	} else {
		alert("One or more of your answers were invalid. Please be sure to enter information in only 2 of the 4 fields.");
	}
}

//1
function one(){
	var distance = document.lenscalc.distance.value
	var horizontal = document.lenscalc.horizontal.value
	var lens_size = document.lenscalc.lens_size.value
	var vertical = document.lenscalc.vertical.value
	
	if ((distance > 0) && (horizontal > 0) && (vertical == 0) && (lens_size == 0)){
		lens_size = distance/horizontal*12.8;
		vertical = horizontal*.75;
		document.lenscalc.lens_size.value = lens_size;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance > 0) && (horizontal == 0) && (vertical == 0) && (lens_size > 0)){
		horizontal = distance/lens_size*12.8;
		vertical = horizontal*.75;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal > 0) && (vertical == 0) && (lens_size > 0)){
		distance = horizontal/12.8*lens_size;
		vertical = horizontal*.75;
		document.lenscalc.distance.value = distance;
		document.lenscalc.vertical.value = vertical;
	} else if ((distance == 0) && (horizontal == 0) && (vertical > 0) && (lens_size > 0)){
		distance = vertical/9.6*lens_size;
		horizontal = vertical/3*4;
		document.lenscalc.distance.value = distance;
		document.lenscalc.horizontal.value = horizontal;
	} else if ((distance > 0) && (horizontal == 0) && (vertical > 0) && (lens_size == 0)){
		horizontal = vertical/3*4;
		lens_size = distance/horizontal*12.8;
		document.lenscalc.horizontal.value = horizontal;
		document.lenscalc.lens_size.value = lens_size;
	} else {
		alert("One or more of your answers were invalid. Please be sure to enter information in only 2 of the 4 fields.");
	}
}//end function