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2d Arrays e FUSSY - Store data in 1d area

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gretty

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2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

hello

I am reading a text file & trying to store some information into a 2d array.

My problem is when I go to store a piece of data into the 1st row (1d area ?

) I get this error

error:

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incompatible types in assignment of `float' to `float[25]'

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For eg, I want to store 25.5 where x is
pur[x][];

My function:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
 
float pur[53][25];   // Purchases Array [week number][purchase no.1, p2, pn...]
 
ifstream infile;
float x;
int count = 0; 
int count2 = 0;
 
while (infile >> x) {
           pur[count] = x;   // error occurs here
 
           while (x!=(char)'\n') {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }
float pur[53][25];   // Purchases Array [week number][purchase no.1, p2, pn...]

ifstream infile;
float x;
int count = 0; 
int count2 = 0;

while (infile >> x) {
           pur[count] = x;   // error occurs here
           
           while (x!=(char)'\n') {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }

Last edited by gretty; Aug 28th, 2009 at 10:24 pm.

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
float pur[53][25];
// ...
pur[count] = x; // error occurs here
float pur[53][25];
// ...
pur[count] = x; // error occurs here

If pur[count] is an array of 25 floats, and x isn't, and you get an error, isn't that enough of a hint? You seem to know how to work it here:

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
pur[count][count2]= x;
pur[count][count2]= x;

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

Improper use of an array,

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
pur[count] = x; // Error
pur[count] = x; // Error

Try,

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
while (infile >> x) {
          if(count2==25) {
                count2=0;
                count++;
          }
      pur[count][count2]= x;
     count2++;
   }
while (infile >> x) {
          if(count2==25) {
                count2=0;
                count++;
          }
      pur[count][count2]= x;
     count2++;
   }

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gretty

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

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Originally Posted by adatapost

Improper use of an array,
Help with Code Tags

C++ Syntax (Toggle Plain Text)
pur[count] = x; // Error
pur[count] = x; // Error
Try,
Help with Code Tags

C++ Syntax (Toggle Plain Text)
while (infile >> x) {
          if(count2==25) {
                count2=0;
                count++;
          }
      pur[count][count2]= x;
     count2++;
   }
while (infile >> x) { if(count2==25) { count2=0; count++; } pur[count][count2]= x; count2++; }

oh, so are you saying that I cannot store 25.5 in where x is - pur[x][]? Is that not possible when I am using a 2d array?

so I cant cant go ...
cout << pur[x];
& it will output 25.5

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

>Is that not possible when I am using a 2d array?
Of course not. You're using a 2D array; you need a row AND a column.

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

Also, from experience. I see that using 2D array to store information
from a file does not always work well. The program might not set
the file content it to proper location. I would suggest to use 1D array.

If 2D is really needed , then use 1D array, and copy it into 2D array.

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      [ Solved by : niek_e, Paul Thompson, SgtMe, murtan, xavier666]
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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

Thanks, lol, I realise now I can do this so I have changed it. But now I have run into another problem.

I am tring to convert x, which is a float into an int. but I get this error

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cannot convert `float' to `const char*' for argument `1' to `int atoi(const char*)'

Is there a way I can fix this without changing x to a 'const char' or 'char', ie, keep it as a float.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
while (infile >> x) {
           count = atoi(x);   // error occurs here again
 
           while (x!=(char)'\n' || count2<=25) {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }
while (infile >> x) {
           count = atoi(x);   // error occurs here again
           
           while (x!=(char)'\n' || count2<=25) {
                 pur[count][count2]= x;
                 count2++;
           }
           count2 = 0;
           count++;
     }

Last edited by gretty; Aug 28th, 2009 at 11:24 pm.

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

•

Originally Posted by firstPerson

Also, from experience. I see that using 2D array to store information
from a file does not always work well. The program might not set
the file content it to proper location. I would suggest to use 1D array.

If 2D is really needed , then use 1D array, and copy it into 2D array.

Thanks

, I agree, 2d arrays are tedius, I wanted to test myself by using one(2d array) in a program but I dont really HAVE to use a 2d array. I am probably going to use a vector because it will be alot more efficient (memory-wise) & alot easier

Last edited by gretty; Aug 28th, 2009 at 11:22 pm.

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Re: 2d Arrays e FUSSY - Store data in 1d area

Aug 28th, 2009

" I am tring to convert x, which is a float into an int. but I get this error"

convert float to int :

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
float pi = 3.14159265;
int pie1 = pi; //implicit conversion from float to int
int pie2 = int(pi); //explicit conversion from float to int, C++ style //recommended
int pie3 = (int)pi; //explicit conversion from float to int, C style
float pi = 3.14159265;
int pie1 = pi; //implicit conversion from float to int
int pie2 = int(pi); //explicit conversion from float to int, C++ style //recommended
int pie3 = (int)pi; //explicit conversion from float to int, C style

you use atoi ( a string to int ). Converts a string to int.

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 C++ Syntax (Toggle Plain Text) 
int i = atoi("100");
int i = atoi("100");

Also atoi is not a good idea. Use the standard sstream header to convert between numbers to string vice-versa.

Last edited by firstPerson; Aug 28th, 2009 at 11:53 pm.

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1) What word becomes shorter if you add a letter to it? 
      [ Solved by : niek_e, Paul Thompson, SgtMe, murtan, xavier666]
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      [*solved by : murtan, xavier666]
3) What is the 123456789 prime numer?

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Join Date: Apr 2009

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gretty

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Re: 2d Arrays e FUSSY - Store data in 1d area

#10

Aug 29th, 2009

thanks guys

Although I am back again with a problem, I have totally overhauled the whole function but it still uses a 2d array.

In the below code, the variable 'count' is never advanced, ie, the if statement never gets called but it should whenever we get to a line break.

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
float x;
 
while (infile >> x) {
 
           if  (x==(char)'\n') {    // this event never happens but it should
                cout << "count advanced\n";
                count++;          
                pCount = 0;
           }    
           else {
                pur[count][pCount]= x;
                pCount++;
           } 
     }
float x;

while (infile >> x) {

           if  (x==(char)'\n') {    // this event never happens but it should
                cout << "count advanced\n";
                count++;          
                pCount = 0;
           }    
           else {
                pur[count][pCount]= x;
                pCount++;
           } 
     }