Question

Help

Answer 1

This is my code so far

Answer 2

#include <iostream>
#include <ctime>
#include <iomanip>
#include<cmath>

using namespace std;
void dividerow(double m[100][100], int n, int r, double val) {
int i;
for (i = 0; i < n+1; i++) {
if(val==0){m[r][i]=false;}
else m[r][i] *= (1/val);

}
}
void dividerow1(double m[100][100], int n, int r, double val){
for(int i =0; i<n+1; i++){
if(val==0){m[r][i]=false;}
else
m[r][i] *= (1/val);
}
}
void dividerow2(double m[100][100], int n, int r, double val){
for(int i =0; i<n+1; i++){
if(val==0){m[r][i]=false;}
else
m[r][i] *= (1/val);
}
}
void dividerow3(double m[100][100], int n, int r, double val){
for(int i =0; i<n+1; i++){
if(val==0){m[r][i]=false;}
else
m[r][i] *= (1/val);
}
}
void dividerow4(double m[100][100], int n, int r, double val){
for(int i =0; i<n+1; i++){
if(val==0){m[r][i]=false;}
else
m[r][i] *= (1/val);
}
}
int main(){

while(1){
int n;
cout << "Enter a number: ";
cin>>n;
double m[100][100];

for (int r=0;r<n;r++){for (int c=0;c<n+1;c++){
m[r][c]=1+rand()%20;}
}

for (int r=0;r<n;r++){for (int c=0;c<n+1;c++){
cout<<m[r][c]<<"\t";}cout<<endl;}
for (int r=n;r>=0;r--){for (int c=n+1;c>=0;c--){
dividerow(m, n, r, m[r][c]);}}
//multadd(m, n, m[0][c], m[1][c]);
for (int r= 1; r<n; r++){
for(int i =0; i<n+1; i++){ // subtract the rows
m[r][i] -= m[0][i];}}

for (int c=n+1;c>0;c--){for (int r=n;r>0;r--){
dividerow1(m, n, r ,m[r][c]);}}

for (int r= 2; r<n; r++){
for(int i =1; i<n+1; i++){
m[r][i] -= m[1][i];}}
for (int c=n+1;c>1;c--){for (int r=n;r>1;r--){
dividerow2(m, n, r, m[r][c]);}}

for (int r= 3; r<n; r++){
for(int i =2; i<n+1; i++){
m[r][i] -= m[2][i];}}
for (int c=n+1;c>2;c--){for (int r=n;r>2;r--){
dividerow2(m, n, r, m[r][c]);}}

for (int r= 4; r<n; r++){
for(int i =3; i<n+1; i++){
m[r][i] -= m[3][i];}}

for (int c=n+1;c>3;c--){for (int r=n;r>3;r--){
dividerow3(m, n, r, m[r][c]);}}

for (int r= 5; r<n; r++){
for(int i =4; i<n+1; i++){
m[r][i] -= m[4][i];}}

Answer 3

cout<<endl;

for (int r=0;r<n;r++){for (int c=0;c<n+1;c++){
cout << setprecision(3)<<m[r][c]<<"\t";}cout<<endl;
}}
return 0;
}

Answer 4

the out put

Answer 5

Enter a number: 3
2 8 15 1
10 5 19 19
3 5 6 6

1 4 7.5 0.5
-0 1 1.6 -0.4
-0 0 1 -0.321
Press any key to continue . . .

Answer 6

im doing linear algebra matrix. and on the second metrix i want to turn 4, 7.5, 1.6 in to zeros without effecting the ones
for more info http://www.math.odu.edu/~bogacki/cgi-bin/lat.cgi?cmd=sys;m1_1=4;m1_2=54;m1_3=64;m1_4=4;m2_1=98;m2_2=49;m2_3=4;m2_4=46;m3_1=26;m3_2=4;m3_3=78;m3_4=12;curn=3;curn=4;vdat=3;vdat=R3;whid=V;whid=1;submit21=Submit&hideops=0

Answer 7

i used this to turn them into zeros but i ran into other problems.. please help this hw was due like a week ago
for (int r=0; r<n;r++){
for(int i =0; i<n; i++){
m[0][i]-=(m[1][i]*m[r][1]);
}}
for (int r=0; r<n;r++){
for(int i =0; i<n+1; i++){
m[1][i]-= (m[2][i]*m[r][2]);
}}
for (int r=0; r<n;r++){
for(int i =0; i<n+1; i++){
m[0][i]-= (m[2][i]*m[r][2]);
}}

Answer 8

help @wio

Answer 9

So you have divide row and subtract row, but need the logic to return the rows to 0s?

Answer 10

yes but whenever i try to turn them in to zeros this is wat i get
Enter a number: 3
2 8 15 1
10 5 19 19
3 5 6 6

1 -1 0 0.5
0 1 -1 1.81
-0 0 1 -0.321
Press any key to continue . . .

Answer 11

i somehow get -1 for first column, second row and second column 3rd row

Answer 12

Here is my guess.
Try this on every row.
```
void zero_cell(double m[10][10], int r, int c) {
int i;
for (i = c; i < n+1; i++) {
m[r][i] = m[r][c] * m[c][i];
}
}

void zero_row(double m[10][10], int r) {
int i;
for (i = r+1; i < n; i++) {
if (m[r][c] != 0) { /* now how you should compare doubles, technically speaking */
zero_cell(m, r, c);
}
}
}
```

Answer 13

How did you get -0 ?

Answer 14

its when it was dividing a negative value to it, the compiler just wrote it as -0

Answer 15

Need to change that `c` to an `i`
```
void zero_cell(double m[10][10], int r, int c) {
int i;
for (i = c; i < n+1; i++) {
m[r][i] = m[r][c] * m[c][i];
}
}

void zero_row(double m[10][10], int r) {
int i;
for (i = r+1; i < n; i++) {
if (m[r][i] != 0) { /* now how you should compare doubles, technically speaking */
zero_cell(m, r, i);
}
}
}
```

Answer 16

Get it to work for one cell, then do it for the whole row, then do that for every column

Answer 17

can you get it to work for one cell?

Answer 18

i get ur code but im a bit confused on how i should combine it to mine

Answer 19

Don't use my code, just try to do something like what I did in your own way.

Answer 20

okay

Answer 21

@wio

Answer 22

i'm still getting similar result as before.
this is how i did it
for (int r=0; r<n;r++){
for(int c =0; c<n+1; c++){
for (int i = r+1; i < n; i++) {

if (m[r][i] != 0) {
for(int i =c; i<n+1; i++)
m[0][i] -= m[1][c] * m[r][1];
}}}}

Answer 23

that not 0 check should happen before your i loop.

Answer 24

you are making it so confusing by not using functions.

Answer 25

if i do that will that not show a syntax error.

Answer 26

on i

Answer 27

sorry, i'm not used to using functions alot

Answer 28

you need to do the check first, with r and c, not r and i

Answer 29

like this
for (int r=0; r<n;r++){
for(int c =0; c<n+1; c++){
if (m[r][c] != 0) {
for (int i = r+1; i < n; i++) {


for(int i =c; i<n+1; i++)
m[0][i] -= m[1][c] * m[r][1];
}}}}

Answer 30

keep trying.

Answer 31

i tried different ways i can think of but, it's still not working @wio

Answer 32

Thanks

Answer 33

for (int r=0; r<n;r++){
for(int c =0; c<n+1; c++){
m[0][c] -= m[1][c] * m[r][1];
if (m[0][1] != 0) {
m[0][1] = m[1][c] * m[r][1];
}}}
@wio This gives me a zero, but when i plug x,y,z to the original matrix, it doesn't give me the right answer, it is off by a bit

Answer 34

Enter a number: 3
2 8 15 1
10 5 19 19
3 5 6 6

1 0 -0 1.22
0 1 -0 1.81
-0 0 1 -0.321
Press any key to continue . . .

when i plug the x,y,z
3*1.22 + 5*1.81 + 6*-.321 = 10.784
i don't get 6 for the outcome

Answer 35

So you know the answer should be 6 and get 10.7?

Answer 36

correct

Answer 37

http://www.math.ncsu.edu/ma114/tools/row_ops.html

Answer 38

use that to get the real answer and compare

Answer 39

Do they really expect you to code this without using functions?

Answer 40

What has your class covered so far?

Answer 41

in this class, the teacher is not really teaching anything, he just give us an assignment to code. a lot of students dropped his class, and i can't switch cuz he is the only one teaching that course

Answer 42

We should do this program with a top down approach.

Answer 43

Do you have a syllabus?

Answer 44

for the assignment, yes

Answer 45

I want to see what you can technically use for this assignment.

Answer 46

I know you can do loops, arrays, etc. But functions and structures?

Answer 47

Linear Algebra Programming. Write a C/C++ program that solves a linear system of n equations and n unknowns. Input: can be generated at random, a matrix of, float m[n][n+1] while n is entered from the key board. Output: a list of n values representing the n unknowns solution.

Answer 48

as far as i know, we can use anything we like, as long as the it is in a loop, and the code work and the values are correct

Answer 49

What do you do if the matrix isn't singular?

Answer 50

i think it has to be singular like i try to do at the top

Answer 51

Can you get that site to work?

Answer 52

it works