Please convert this c program into matlab code

Question

PULAK Kumer 2020-11-26

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https://ww2.mathworks.cn/matlabcentral/answers/663168-please-convert-this-c-program-into-matlab-code

回答： PULAK Kumer 2020-11-26

#include<stdio.h> #include<math.h> int main() { float x[10],y[15][15]; int n,i,j; printf("Enter n : "); scanf("%d",&n); printf("X\tY\n"); for(i = 0;i<n;i++){ scanf("%f %f",&x[i],&y[i][0]); } //forward difference table for(j=1;j<n;j++) for(i=0;i<(n-j);i++) y[i][j] = y[i+1][j-1] - y[i][j-1]; printf("\n***********Forward Difference Table *********\n"); //display Forward Difference Table for(i=0;i<n*2-1;i++) { int indx = i/2; printf("\t"); if(!(i%2)) printf("%.2f",x[indx]); int j_max = (n>i)? i : n*2-i-1; for(j=0;j<=j_max;j++) { printf("\t"); if(i%2 == j%2) printf("%.2f",y[indx-j/2][j]); } printf("\n"); }

return 0; }

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Answer 1

Walter Roberson 2020-11-26

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That code cannot be converted to MATLAB: it depends on standard input for reading from the user, but MATLAB does not have standard input.

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Walter Roberson 2020-11-26

在 MATLAB Online 中打开

My guess at the formatting of the original code would be

#include<stdio.h>
#include<math.h>
int main()
{
    float x[10],y[15][15];
    int n,i,j;
    printf("Enter n : ");
    scanf("%d",&n);
    printf("X\tY\n");
    for(i = 0;i<n;i++)
    {
      scanf("%f %f",&x[i],&y[i][0]);
    } //forward difference table
    for(j=1;j<n;j++)
      for(i=0;i<(n-j);i++)
          y[i][j] = y[i+1][j-1] - y[i][j-1];
          
    printf("\n***********Forward Difference Table *********\n"); //display Forward Difference Table
    for(i=0;i<n*2-1;i++)
    {
      int indx = i/2;
      printf("\t");
      if(!(i%2))
          printf("%.2f",x[indx]);
      int j_max = (n>i)? i : n*2-i-1;
      for(j=0;j<=j_max;j++)
      {
          printf("\t");
          if(i%2 == j%2)
              printf("%.2f",y[indx-j/2][j]);
      }
      printf("\n");
    }
    return 0;
}

(Remember that in C, there is no explicit end for equivalent unless you deliberately use { } to group statements, so the for i, for j, y[i][j] set of lines is a complete double-nested loop that does not extend further -- the printf after is not inside the loops.)

PULAK Kumer 2020-11-26

编辑：Walter Roberson 2020-11-26

在 MATLAB Online 中打开

If this code was started from index 1(array index) instead of 1 then what will be done for the following part?

for(i=0;i<n*2-1;i++) { int indx = i/2; printf("\t"); if(!(i%2)) printf("%.2f",x[indx]); int j_max = (n>i)? i : n*2-i-1; for(j=0;j<=j_max;j++) { printf("\t"); if(i%2 == j%2) printf("%.2f",y[indx-j/2][j]); } printf("\n"); }

Walter Roberson 2020-11-26

在 MATLAB Online 中打开

OFFSET = 1;
for i=0 : n*2-2
    indx = floor(i/2);
    fprintf("\t");
    if mod(i,2) == 0
        fprintf("%.2f",x(indx+OFFSET));
    end
    if n > i
        j_max = i;
    else
        j_max = n*2-i-1;
    end
    for j = 0 : j_max
        fprintf("\t");
        if mod(i,2) == mod(j,2)
          fprintf("%.2f", y(indx-j/2+OFFSET, j+OFFSET));
        end
        printf("\n");
    end
end

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Answer 2

PULAK Kumer 2020-11-26

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https://ww2.mathworks.cn/matlabcentral/answers/663168-please-convert-this-c-program-into-matlab-code#answer_556738

在 MATLAB Online 中打开

What is the wrong for the following code:

clc;
 clear all;
 close all;
  
fprintf('\n************************************************************');
fprintf('\n****************** NIRALI PUBLICATIONS *********************');
fprintf('\n******** CONM by M. T. Puranik & V. N. Chougule ************');
fprintf('\n*** Interpolation by Newtons Forward Difference Formula  ***');
fprintf('\n************************************************************');
n = input('\nEnter number of data points = ');
h = input('\nEnter step size (h) = ')
x(1) = input('\nx0 = ');
y(1) = input('y0 = ');
for i=2:n
    x(i)=x(i-1)+h;
    fprintf('\nX%d = %f',i,x(i));
    fprintf('\t\tY%d: ',i);
    y(i) = input('');
end
x_reqd = input('\nEnter X for which value of Y is sought: ');
s=(x_reqd-x(1))/h;
for i=1:n
    diff(i,1)=y(i);
end
%% Calculate Forward Differance Table
for j=2:n
    for i=1:n-j+1
        diff(i,j)=diff(i+1,j-1)-diff(i,j-1);
    end
end
fprintf('\n\t   Forward Differance Table');
fprintf("\n");
fprintf("============================================================================")
fprintf("\n");
fprintf("x\t\t\ty\t\t\tdy");
        for j=2:1:n-1
       fprintf("\t\t\t");
            fprintf("D%dy",j);
           
        end
         fprintf("\n");
        fprintf("============================================================================")
  
       
%% Print Forward Differance Table
offset=1;
for i=0:n*2-2
 index=floor(i/2);
    fprintf("\t\t")
    if mod(i,2)==0
       fprintf('\n %.6f',x(index+offset));   
    end
 if n>i
     j_max=i
 else
     j_max=n*2-i-1
 end
 
    for j=0:j_max
        if mod(i,2)==mod(j,2)
  
        fprintf('\t\t%.6f',diff(index-j/2+offset,j+offset));
        end
    end
end