I'm wondering if is there a way to summarize the results of probability that I got through a loop? So I can know how many successful hits there were, given x number of attempts. Right now I just get a stream of 1 or 0 statements (1 for a successful hit, 0 for fail), not very practical. It looks like this:
public class doGry {
public static void main(String[] args ) {
for (int i = 0; i < 50; i++) {
// chance to hit (h) = 35% + (ma - md)
// 8% < h < 90%
double ma = 20;
double md = 10;
double probability;
System.out.println("probability of success " + (probability = 35 + (ma - md)));
double probab2 = probability / 100;
double r = Math.random();
int roll;
if (r <= probab2) roll = 1;
else roll = 0;
System.out.println(roll);
}
}
}
There are few variables that can be initialized outside of for-loop since you are not modifying its value, so no need it initialize it again and again.
Using a variable count, for keeping track of successful hits. For each successful hit, increment its value by 1.
public class doGry {
public static void main(String[] args ) {
double ma = 20;
double md = 10;
double probability = 35 + (ma - md);
double probab2 = probability / 100;
int count = 0;
for (int i = 0; i < 50; i++) {
System.out.println("probability of success " + probability);
double r = Math.random();
if (r <= probab2)
{
System.out.println("1");
count++;
}
else
System.out.println("0");
}
System.out.println("Succesful hits " + count);
}
}
All you have to do is add in a variable to keep track of how many successful rolls occurred, and then divide that by the total number of rolls using a double like so
public class doGry
{
public static void main(String[] args )
{
int total = 0;
for (int i = 0; i < 50; i++)
{
// chance to hit (h) = 35% + (ma - md)
// 8% < h < 90%
double ma = 20.0;
double md = 10.0;
double probability;
System.out.println("probability of success " + (probability = 35 + (ma - md)));
double probab2 = probability / 100;
double r = Math.random();
int roll;
if (r <= probab2) {roll = 1; total++;}
else roll = 0;
System.out.println(roll);
}
System.out.println("total: " + total/50.0);
}
}
Notice in the final System.out.println statement, the total is being divided by 50.0 (and not 50) as the .0 indicates you want a double division and not integer division, the latter of which throws away any remainder decimal values.
I'm a totally novice programmer, and I'm pretty confused by how to use printf. The use of printf in my code is at the end of the paymentCalc method; I'm trying to print data to a line, specify 2 decimal points to print, and pad it 10 spaces before printing the next output.
The code isnt formatting at all. What am I doing wrong here? It's all printing on the same line, but it's printing a million decimals, and it doesnt seem to be padding properly.
/*
* Step 1: Get starting annual interest rate
* Step 2: Get ending annual interest rate
* Step 3: Get increment rate
* Step 4: Get First # of years for repayment
* Step 5: Get Last # of years for repayment
* Step 6: Get # of years to increment by
* Step 7: Get loan amount
*
* Convert annual rates to monthly rates MIR = Annual rate/12
* MTP = # of years * 12
*
* MIR = monthly interest rate
* MTP = months to pay
* Annuity Factor =(mir*(1+mir)^mtp)/(((1+mir)^mtp)-1)
* Payment = Amount Loaned * Annuity Factor
*
*
* Produce a list of possible loan payments
* Based on a series of annual interest rates
* Start at user entered rate and increment until it hits user entered max
* Display annual payment as monthly payments
* */
import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
public class methodshomework {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
//VARIABLES
//amounts in years
double startAnnInt = 0;
double endAnnInt = 0;
double incRate = 0;
double incRatePercent = 0;
double firstYears = 0;
double lastYears = 0;
double incYears = 0;
double loanAmt = 0;
//amounts in months
double startMonthInt = 0;
double endMonthInt = 0;
double monthIncRate = 0;
double firstMonths = 0;
double lastMonths = 0;
double incMonths = 0;
double monthIncRatePercent = 0;
double annIncRatePercent = 0;
System.out.println("Hello, and welcome to the loan calculator");
//Acquire necessary data
System.out.println("What is the starting annual interest rate? (please enter as XX, where XX = XX%)");
startAnnInt = (scanner.nextDouble()/100);
System.out.println("What is the ending annual interest rate? (please enter as XX, where XX = XX%)");
endAnnInt = (scanner.nextDouble()/100);
System.out.println("What is the annual increment rate? (please enter as XX, where XX = XX%)");
incRate = (scanner.nextDouble()/100);
System.out.println("What is the first term for payment (in years)?");
firstYears = scanner.nextDouble();
System.out.println("What is the last term for payment (in years)?");
lastYears = scanner.nextDouble();
System.out.println("What is the term increment (in years)?");
incYears = scanner.nextDouble();
System.out.println("What is the loan amount? (in the form XXXXXX, where XXXXXX = $XXX,XXX)");
loanAmt = scanner.nextDouble();
double[] monthArray = yearToMonth(firstYears, lastYears, incYears, startAnnInt, endAnnInt, incRate);
firstMonths = monthArray[0];
lastMonths = monthArray[1];
incMonths = monthArray[2];
startMonthInt = monthArray[3];
endMonthInt = monthArray[4];
monthIncRate = monthArray[5];
monthIncRatePercent = monthArray[6];
annIncRatePercent = monthArray[7];
paymentCalc(startMonthInt, endMonthInt, monthIncRate, firstMonths, lastMonths, incMonths, loanAmt, firstYears, lastYears, incYears, startAnnInt, endAnnInt, incRate);
}
//MODULES HERE
public static double[] yearToMonth(double firstYears, double lastYears, double incYears, double startAnnInt, double endAnnInt, double incRate){
double firstMonths = 0;
double lastMonths = 0;
double incMonths = 0;
double startMonthInt = 0;
double endMonthInt = 0;
double monthIncRate = 0;
double monthIncRatePercent = 0;
double annIncRatePercent = 0;
//do our conversions
firstMonths = (firstYears * 12);
lastMonths = (lastYears * 12);
incMonths = (incYears * 12);
startMonthInt = (startAnnInt / 12);
endMonthInt = (endAnnInt / 12);
monthIncRate = (incRate / 12);
monthIncRatePercent = (monthIncRate/100);
annIncRatePercent = (incRate/100);
//put our conversions into an array
double[] monthArray = {firstMonths, lastMonths, incMonths, startMonthInt, endMonthInt, monthIncRate, monthIncRatePercent, annIncRatePercent};
//return our conversions
return monthArray;
}
public static void paymentCalc(double startMonthInt, double endMonthInt, double monthIncRate, double firstMonths, double lastMonths, double incMonths, double loanAmt, double firstYears, double lastYears, double incYears, double startAnnInt, double endAnnInt, double incRate){
double monthInt = 0;
double monthsToPay = 0;
double rowNumber = (((lastYears - firstYears))/incYears);
double rowNumberWithInt = (rowNumber + 1);
double colNumber = ((endMonthInt - startMonthInt)/monthIncRate);
double colNumberWithTop = (colNumber+1);
double currentYears = 0;
double currentMonths = 0;
double currentMonthInt = 0;
double currentPayment = 0;
double currentAnnInt = 0;
double annuityAmt = 0;
//counting columns
for (double i = 0; i <= colNumberWithTop; i++) {
//printing the top column
if (i == 0){
System.out.printf("%-10s", "Interest Rate");
for (double k = 0; k <= rowNumber; k++) {
currentYears = (firstYears + (incYears * i));
System.out.printf("%10s", currentYears + " Years"); }
} else if (i > 0) {
//finding annual interest rate for printing, and monthly interest rate as a decimal for math
currentAnnInt = (startAnnInt + (incRate * i));
currentMonthInt = ((currentAnnInt/100)/12);
System.out.printf("%.2f10s\n", (currentAnnInt * 100));
for (double k = 0; k <= rowNumber; k++) {
monthsToPay = (startMonthInt + (monthIncRate * i));
annuityAmt = annuityCalc(currentMonthInt, monthsToPay);
currentPayment = (loanAmt * annuityAmt);
System.out.printf("%.2f10s", currentPayment);
}
}
}
}
public static double annuityCalc(double monthInt, double monthsToPay){
double annuityFactor = 0;
double mirPow = 0;
mirPow = Math.pow((1+monthInt), monthsToPay);
annuityFactor = ((monthInt*mirPow)/(mirPow-1));
return annuityFactor;
}
}
EDIT:
I changed the code to
for (double i = 0; i <= colNumberWithTop; i++) {
//printing the top column
if (i == 0){
System.out.printf("%10", "Interest Rate");
for (double k = 0; k <= rowNumber; k++) {
currentYears = (firstYears + (incYears * i));
System.out.printf("%10", currentYears + " Years"); }
} else if (i > 0) {
//finding annual interest rate for printing, and monthly interest rate as a decimal for math
currentAnnInt = (startAnnInt + (incRate * i));
currentMonthInt = ((currentAnnInt/100)/12);
System.out.printf("%10.2f\n", currentAnnInt);
for (double k = 0; k <= rowNumber; k++) {
monthsToPay = (startMonthInt + (monthIncRate * i));
annuityAmt = annuityCalc(currentMonthInt, monthsToPay);
currentPayment = (loanAmt * annuityAmt);
System.out.printf("%10.2f", currentPayment);
}
And it's now giving me "java.util.UnknownFormatConversionException: Conversion = '1'"
EDIT 2:
I've changed the code to
public static void paymentCalc(double startMonthInt, double endMonthInt, double monthIncRate, double firstMonths, double lastMonths, double incMonths, double loanAmt, double firstYears, double lastYears, double incYears, double startAnnInt, double endAnnInt, double incRate){
double monthInt = 0;
double monthsToPay = 0;
double rowNumber = (((lastYears - firstYears))/incYears);
double rowNumberWithInt = (rowNumber + 1);
double colNumber = ((endMonthInt - startMonthInt)/monthIncRate);
double colNumberWithTop = (colNumber+1);
double currentYears = 0;
double currentMonths = 0;
double currentMonthInt = 0;
double currentPayment = 0;
double currentAnnInt = 0;
double annuityAmt = 0;
//counting columns
for (double i = 0; i <= colNumberWithTop; i++) {
//printing the top column
if (i == 0){
System.out.printf("%-20s", "Interest Rate");
for (double k = 0; k <= rowNumber; k++) {
currentYears = (firstYears + (incYears * i));
System.out.printf("%-20s", currentYears + " Years");
}
System.out.println();
} else if (i > 0) {
//finding annual interest rate for printing, and monthly interest rate as a decimal for math
currentAnnInt = (startAnnInt + (incRate * i));
currentMonthInt = ((currentAnnInt/100)/12);
System.out.printf("%-20.2f%%", currentAnnInt*100);
for (double k = 0; k <= rowNumber; k++) {
monthsToPay = (firstMonths + (incMonths * i));
annuityAmt = annuityCalc(currentMonthInt, monthsToPay);
currentPayment = (loanAmt * annuityAmt);
System.out.printf("%-20.2f", currentPayment);
}
System.out.println();
}
}
}
The data I'm getting back is
Interest Rate 15.0 Years 15.0 Years 15.0 Years 15.0 Years
4.25% 28235795.88 28235795.88 28235795.88 28235795.88
4.50% 26667168.53 26667168.53 26667168.53 26667168.53
4.75% 25263659.87 25263659.87 25263659.87 25263659.87
5.00% 24000502.07 24000502.07 24000502.07 24000502.07
5.25% 22857645.03 22857645.03 22857645.03 22857645.03
5.50% 21818684.11 21818684.11 21818684.11 21818684.11
5.75% 20870067.61 20870067.61 20870067.61 20870067.61
6.00% 20000502.50 20000502.50 20000502.50 20000502.50
6.25% 19200502.59 19200502.59 19200502.59 19200502.59
>
Why on earth is it doing this? It seem to be printing the interest rate under the 30 Years column and shifting all the other columns left one, and printing the first interest rate at the end of the top column
Expected output is
Interest Rate 15 Years 20 Years 25 Years 30 Years
4.0000 739.69 605.98 527.84 477.42
4.2500 752.28 619.23 541.74 491.94
4.5000 764.99 632.65 555.83 506.69
4.7500 777.83 646.22 570.12 521.65
5.0000 790.79 659.96 584.59 536.82
5.2500 803.88 673.84 599.25 552.20
5.5000 817.08 687.89 614.09 567.79
5.7500 830.41 702.08 629.11 583.57
6.0000 843.86 716.43 644.30 599.55
Issue was that when I asked you to remove the s you removed everywhere...
This should work now
for (double i = 0; i <= colNumberWithTop; i++) {
//printing the top column
if (i == 0){
System.out.printf("%-10s", "Interest Rate");
for (double k = 0; k <= rowNumber; k++) {
currentYears = (firstYears + (incYears * i));
System.out.printf("%10s", currentYears + " Years");
}
System.out.println();
} else if (i > 0) {
//finding annual interest rate for printing, and monthly interest rate as a decimal for math
currentAnnInt = (startAnnInt + (incRate * i));
currentMonthInt = ((currentAnnInt/100)/12);
System.out.printf("%10.2f%%", currentAnnInt*100);
for (double k = 0; k <= rowNumber; k++) {
monthsToPay = (startMonthInt + (monthIncRate * i));
annuityAmt = annuityCalc(currentMonthInt, monthsToPay);
currentPayment = (loanAmt * annuityAmt);
System.out.printf("%10.2f", currentPayment);
}
System.out.println();
EDITED per OP's request.
PrintStream#printf takes in a format string and objects, returning a formatted string. The format string has a certain format for numeric values:
%[argument_index$][flags][width][.precision]conversion
For example, to have a number take up 15 characters and have 2 decimal places, the follow format string would do the job:
%15.2f.
In your edit, you are missing the conversion portion of the formatted string. This is causing the UnknownFormatConversionException. Each format string MUST end with a conversion (d, f, b, s).
For example, change:
System.out.printf("%10", currentYears + " Years");
to:
System.out.printf("%10s", currentYears + " Years");
Notice the s at the end of the format string. Read more about the format string syntax at the official documentation.
I am trying calculating the term for Pi using the Taylor series. I want to keep adding terms until the last value of term is less than 1e-17. I have set the program right now at term = 31 because after that there is no change Pi = 3.141592653589794 error = 8.88178e - 16.
public static double compPi()
{
int terms1 = 31;
int sg = 1, denom1 = 1;
double sum = 1.0, denom2 = 1.0;
for (int t = 2; t <= terms1; t++){
denom1 += 2; denom2 *= 3;
double term = 1.0/ (denom1 * denom2);
sg *= -1;
sum += sg * term;
}
double pi = Math.sqrt(12) * sum;
return pi;
}
As Louis Wasserman suggested you are running into precision limitations with doubles in Java. Consider using BigDecimals for your calculations for more precision.
The floating-point errors in your sum are adding up to that difference, simply reverse your iteration (t = 31..2, i.e. start by adding up the very small summands first) and the error goes away:
public static double compPiReversed()
{
int terms1 = 31;
int sg = -1;
double sum = 0;
for (int t = terms1; t >= 2; --t) {
int denom1 = 1 + (t-1) * 2;
double denom2 = Math.pow(3, t-1);
double term = 1.0 / (denom1 * denom2);
sg *= -1;
sum += sg * term;
}
sum += 1;
double pi = Math.sqrt(12) * sum;
return pi;
}
again the 31st summand won't actually contribute (try starting at terms1 = 30, don't forget to change the sign sg = 1, too.)
I am trying to write a program which asks the user for a series of positive values and computes the mean and standard deviation of those values having the input stop when the user enters -1. I seem to have the average part down however. I can't seem to get the standard deviation.
So far this is what I have.
import java.util.Scanner;
public class HW0402
{
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
double x;
double sum = 0;
double average = 0;
double dev = 0;
double var = 0;
double sqrx = 0;
int n = 0;
do
{
System.out.println("Enter positive values, enter -1 to end");
x = input.nextInt();
if (x == -1)
{
break;
}
sum += x;
n++;
average = sum / n;
sqrx += Math.pow(x-average,2);
var = sqrx / (n-1);
dev = Math.sqrt(var);
} while (x != -1);
System.out.println("Average: " + average);
System.out.println("Deviation: " + dev);
}
}
I seem to get odd results such as decimals when simply calculating sqrx += x- average
I'm new to java and haven't leaned alternatives to this problem, I would love it if someone pointed me in the right direction on what I should do, or explain what I did wrong.
Apologies ahead of time for any novice mistakes I made.
int n = 0;
int K = 0;
double Sum = 0;
double Sum_sqr = 0;
do {
System.out.println("Enter positive values, enter -1 to end");
x = input.nextInt();
if (x == -1)
{
break;
}
if ( n == 0 ) K = x;
n++;
Sum += (x - K);
Sum_sqr += (x - K) * (x - K);
} while (x != -1);
double mean = K + Sum / n;
double varPop = (Sum_sqr - (Sum*Sum)/n) / (n);
double varSample = (Sum_sqr - (Sum*Sum)/n) / (n-1);
double devPop = Math.sqrt(varPop);
double devSample = Math.sqrt(varSample);
Reference Wikipedia: Computing Shifted Data. Also, Population or Sample, makes a difference.
How would I finish this program?
I know it is wrong where I have inputed the calculation into the code. What do I need to change to get the program to work the way the assignment asks (see image)? Also where would I loop it to recalculate if the user chooses to at the end?
package cosx;
import java.util.Scanner;
public class cosx2 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter the degree: ");
double degree = input.nextDouble();
double radian = getRadian(degree);
calculateCos(input, radian,degree);
}
public static double getRadian(double x) {
return x = (Math.PI/180)*x;
}
private static void calculateCos(Scanner std, double rad, double deg) {
System.out.print("How many terms do you want to calculate the cos: ");
int terms = std.nextInt();
double top;
double bottom;
double sum=0;
for(int i = 0; i<= terms; ++i){
top = Math.pow(-1, i);
bottom =1;
int repeat = 2*i+1;
for(int j = 1; j <= repeat; ++j){
bottom *= j;
}
if(i%2 == 0)
sum += (top/bottom);
else
sum -= (top/bottom);
}
System.out.printf("The sin (%.1f", deg);
System.out.printf(") is %.6f", sum);
}
}