need help with sin(x) and bar graph

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  1. #1
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    need help with sin(x) and bar graph

    Instructions:
     You may use the template to organize your program.
     No input from user is required.
     x & y are float.
     The function sin(x) is in the math.h header file and requires radians as input.
     Must use a for loop.
     Output MUST print to a file. However, you may also print to the screen.
     Print a horizontal y axis using -. (Outside loop)
     Print a vertical x axis using |. (Inside loop)
     After finding the y value, print a scaled number of stars to represent y (inside loop).
    Refer to bar graph code on p. 108.
     Avoid mixed mode expressions.
     Follow order of operations and precedence of operators.

    i cant seem to figure out how to print all the stars in the sin(x) "shape" on x/y line when it prints to a file....i just need the top portion of the sin(x), help!
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    
    main()
    {
       const float pi=3.1459;
       float x=pi,                   /*values for x in radians*/
             y=.0437;                    /*outputted number of stars*/
    
    
       int stars,
           i =0.0;      /*number of stars graphed*/
    
       FILE*joser=NULL;
    
    
       if((joser=fopen("c:outputfilename.txt","w")) ==NULL)
            printf("Error opening data file./n");
       else
       {
          for(i=0.0; i<=50.0;++i)
    
            fprintf(joser,"_");
            fprintf(joser,"y\n");
    
            {
               for(x=0.0 ;x<=20.0;++x)
    
               fprintf(joser,"|\n");
    
            }
          y=sin(x);
          stars=(y*50+.5);
          for(y=0.0; x<=stars;++x)
    
          fprintf(joser,"*");
    
       }
       fprintf(joser,"|\nx");
    
       fclose(joser);
    
    
    
    
          system("PAUSE");
          return 0;
    }

  2. #2
    Frequently Quite Prolix dwks's Avatar
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    Code:
    const float pi=3.1459;
    Why not
    Code:
    double pi = atan(1) * 4;
    or 3.14159265358979...

    Code:
    printf("Error opening data file./n");
    No doubt you meant \n, not /n.

    Code:
            fprintf(joser,"_");
            fprintf(joser,"y\n");
    Does that really warrant two calls to fprintf()? . . . and did you mean something like this?
    Code:
    fprintf(joser, "_&#37;f\n", y);
    Code:
    for(x=0.0 ;x<=20.0;++x)
    Using floating point numbers to control a loop is a bad idea for accuracy reasons, especially when you're not using the loop variable in the loop body itself.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  3. #3
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    well, im fiddling around with the code and i think im almost there, i just need to make it so that when it writes to a .txt file, it prints out an X and Y lines along with STARS that resemeble the SIN(x) graph, just the top portion, but all i get are just plain stars all the same lengths....this is what the program is supposed to do, print to a .txt file this:
    _________y
    |*
    |**
    |***
    |****
    |***
    |**
    |*
    x


    except supposed to be around as long as the Y graph....how do i calculate it into this code???This program should graph the funcion y=sin(x)
    on the interval from 0 to pi in incriments of pi/20.
    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <math.h>
    
    main()
    {
       const float pi=3.1459;
       float x,                   /*values for x in radians*/
             y;                    /*outputted number of stars*/
    
       int stars,
           i =0.0;      /*number of stars graphed*/
    
       FILE*fptr=NULL;
    
    
       if((fptr =fopen("c:outputfilename.txt","w")) ==NULL)      /*test if files opened correctly*/
          printf("\nError opening file\n\n");
       else
       {
          for(i=1; i<=60; ++i)                                   /*for loop to print the y axis*/
             fprintf(fptr,"_");
          fprintf(fptr," Y\n");
    
    
    
          for(x=0; x<=20.0; ++x)                            /*for loop to calculate the function*/
          {                                                /*values and the number of stars*/
             int g;
             g=sin(x*pi+1);
             fprintf(fptr,"|");                                /*prints the x-axis*/
    
    
             for(y=g ;y<=20.0;++y)                   /*for loop to print the stars*/
                fprintf(fptr,"*");
             fprintf(fptr,"\n");         /*go to new line after printing a row*/
          }                              /*of stars*/
          fprintf(fptr,"|\n|\nX");
    
          fclose(fptr);
       }
    
       system("pause");
       return 0;
    }
    Last edited by SuPaNooB; 10-07-2007 at 01:21 AM.

  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Code:
    if((fptr =fopen("c:outputfilename.txt","w")) ==NULL)
    I never understood the rationale behind using full path names with fopen(). Just use the current directory! It's shorter and it's more convenient for the user. It' more portable: maybe you only have write access to the current directory. Maybe there isn't a c: drive, or the main drive is d: or something. Maybe the user doesn't want a file called outputfilename.txt suddenly appearing on the root of their drive. Maybe the user is running Linux, in which case fopen() will balk at that strange-looking filename, or you'll get a file called 'c:outfilefilename.txt'.

    Now that that rant's out of the way . . .

    Code:
             int g;
             g=sin(x*pi+1);
    Who gave you that algorithm? Because it's not right.

    What you want is for the parameter to sin to vary from 0 to PI, so that you get that sine-curve you're looking for. Since x goes from 0 to 20, you need to divide x by 20, to get it to vary from 0 to 1, and then multiply that by PI, so that it varies from 0 to PI, which is what you want.

    Okay. Now the return value of sin() will be from 0 to 1. Since you want a bar graph that is (presumably) 60 wide, you need to multiply the return value of sin by 60.

    In other words:
    Code:
    g = sin(x * pi / 20.0) * 60.0;
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

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    Projects: codeform, xuni, atlantis, nort, etc.

  5. #5
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    Code:
             stars=sin(x*pi/20)*60;
    
             for(y=stars;y<=60;++y)                   /*for loop to print the stars*/
                fprintf(fptr,"*");
             fprintf(fptr,"\n");         /*go to new line after printing a row*/
    this is all that i changed, i forgot that i created "stars" so i took out g and replaced it with stars....

    well, you gave me a pretty good idea on it, once i modified that graph, and ran the program, i got pretty damn close to what the txt file was supposed to look like now when i run it, i get

    Code:
    ____________________________________________________________ Y
    |*************************************************************
    |****************************************************
    |*******************************************
    |**********************************
    |**************************
    |*******************
    |*************
    |********
    |****
    |**
    |**
    |**
    |****
    |********
    |*************
    |*******************
    |**************************
    |**********************************
    |*******************************************
    |****************************************************
    |*************************************************************
    |
    |
    X
    the curving is quite good, EXCEPT its supposed to be in a mountain shape, not caved in...lolz, but other than that, the coding is almost there....now i have to figure out how to reverse the arrangement of the stars to get my


    **
    ***
    *****
    ******
    *******
    ******
    *****
    ***
    **


    any thoughts?

  6. #6
    Frequently Quite Prolix dwks's Avatar
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    Code:
    for(y=stars;y<=60;++y)
    ->
    Code:
    for(y=0;y<=stars;++y)
    perhaps?
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

  7. #7
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    Quote Originally Posted by dwks View Post
    Code:
    for(y=stars;y<=60;++y)
    ->
    Code:
    for(y=0;y<=stars;++y)
    perhaps?
    thank you dwks, your help was quite enlightening, taking my programming "c" class, once a day per week for three hours doesnt quite make it into getting what i need to learn, even though i do come up with most of the code, you helped me finish it, thank you again...

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