calculating the mode

bigggame · 06-12-2006, 12:18 AM

Hi there,

So I have a 10 element array of int's and I need to calculate the mode.

I haven't written any code (for the calculation part) because I have no idea where to start. I was just hoping someone who has done this before or thinks they have a good idea could point me in the right direction, I would appreciate it.

Is there a function to do this for me in math.h?

bivhitscar · 06-12-2006, 12:29 AM

The mode is just the average, should be pretty easy. I'd suggest trying it out first and then come here with a specific problem if you get stuck.

bigggame · 06-12-2006, 12:36 AM

Hey, thanks i appreciate any help i can get..

I'm looking for:

"the value that appears most frequently in the values input by the user."

Is there a sorting function that checks for repeat input?

bivhitscar · 06-12-2006, 12:42 AM

Oh crap, it is to, sorry about that. Still, you could at least write a loop or something, just to show us that you're trying. We like to help, but not without some effort from you first.

jafet · 06-12-2006, 02:27 AM

You could sort the data, then loop through it looking for the longest string of repeat values.

**Bubba** · 06-12-2006, 04:58 AM

Code:

for (int i=0;i<10;i++)
{
  //Do some stuff here
}

bigggame · 06-12-2006, 08:38 AM

ok, ok sorry guys don't hate me i was thinking of something like this (keep in mind I already ordered the entries from smallest to largest):

Code:

void compute_mode(char test_scores[],int *n_scores)
{
int i, j,k;
char mode[*n_scores];
int n_modes = 1;

for(i=o;i<*n_scores;i++)
{
  for(j=i+1;j<*n_scores;j++) 
  {
    if( test_scores[i] < test_scores[j] )
      continue;
    else 
      {
       mode[n_modes] = test_scores[i];
       n_modes++;
       }
    }
}

for(k = 0; k <n_modes; k++)
   {
   printf("Mode %s", mode);
   }
}

dwks · 06-12-2006, 04:13 PM

Code:

printf("Mode %s", mode[]);

That won't work.

test_score isn't the same variable as test_scores.

**Salem** · 06-13-2006, 01:18 AM

> i was thinking of something like this
Close enough - now write something which actually compiles.

> char mode[*n_scores];
C doesn't (yet) support variable length arrays.

> for(i=o;i<*n_scores;i++)
I guess that o was meant to be 0 (zero)

quzah · 06-13-2006, 01:44 AM

Quote:

Originally Posted by Salem

> char mode[*n_scores];
C doesn't (yet) support variable length arrays.

C99 does. Your compiler on the other hand...

Quzah.

jafet · 06-13-2006, 03:04 AM

You can make it simpler. A whole lot simpler, in fact:

Let's say you want to find the mode of 0,0,1,1,1,2,4,5,5,5,5,6,7,7,8,10. Let's call a row of consecutive numbers (like 3,3,3) a "run". You can proceed thus:

We start with 0, because it is the first element. We find that the run of 0s is of length 2. This is the longest run so far.

We proceed to the next element, 1, which has a run of three elements. This is longer than the zero run, so we store this as the longest run instead. The length of the 0s run is forgotten, as it is not needed.

... ...

In the end, 5 is found to be the mode, as it has a run of 5. The trick is that finding the mode only requires that you keep track of the longest run SO FAR, while ignoring those runs shorter than the longest run found so far. After you've checked all the runs, the longest run so far is guaranteed to be your mode, because you've found the longest run in the whole array.

Tip: you will only need a loop counter, two variables to keep track of the longest run found, and two more to keep track of the current run. You will only need to run through the whole array once.

06-12-2006, 12:18 AM	#1
bigggame Registered User Join Date: Jun 2006 Posts: 4	calculating the mode Hi there, So I have a 10 element array of int's and I need to calculate the mode. I haven't written any code (for the calculation part) because I have no idea where to start. I was just hoping someone who has done this before or thinks they have a good idea could point me in the right direction, I would appreciate it. Is there a function to do this for me in math.h?
bigggame is offline

06-12-2006, 12:29 AM	#2
bivhitscar Awesomefaceradcore Join Date: Apr 2006 Location: Melbourne, Australia Posts: 186	The mode is just the average, should be pretty easy. I'd suggest trying it out first and then come here with a specific problem if you get stuck. __________________ it's ironic considerate rarity patron of love higher knowledge engulfs me...
bivhitscar is offline

06-12-2006, 12:36 AM	#3
bigggame Registered User Join Date: Jun 2006 Posts: 4	Hey, thanks i appreciate any help i can get.. I'm looking for: "the value that appears most frequently in the values input by the user." Is there a sorting function that checks for repeat input?
bigggame is offline

06-12-2006, 12:42 AM	#4
bivhitscar Awesomefaceradcore Join Date: Apr 2006 Location: Melbourne, Australia Posts: 186	Oh crap, it is to, sorry about that. Still, you could at least write a loop or something, just to show us that you're trying. We like to help, but not without some effort from you first. __________________ it's ironic considerate rarity patron of love higher knowledge engulfs me...
bivhitscar is offline

06-12-2006, 04:58 AM	#6
Bubba Super Moderator Join Date: Aug 2001 Posts: 7,819	Code: for (int i=0;i<10;i++) { //Do some stuff here }
Bubba is offline

06-12-2006, 04:13 PM	#8
dwks Frequently Quite Prolix Join Date: Apr 2005 Location: Canada Posts: 7,698	Code: printf("Mode %s", mode[]); That won't work. test_score isn't the same variable as test_scores. __________________ 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.
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06-13-2006, 01:18 AM	#9
Salem and the hat of Jobseeking Join Date: Aug 2001 Location: The edge of the known universe Posts: 21,710	> i was thinking of something like this Close enough - now write something which actually compiles. > char mode[n_scores]; C doesn't (yet) support variable length arrays. > for(i=o;i<n_scores;i++) I guess that o was meant to be 0 (zero) __________________ If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
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06-13-2006, 03:04 AM	#11
jafet Registered User Join Date: Mar 2006 Posts: 726	You can make it simpler. A whole lot simpler, in fact: Let's say you want to find the mode of 0,0,1,1,1,2,4,5,5,5,5,6,7,7,8,10. Let's call a row of consecutive numbers (like 3,3,3) a "run". You can proceed thus: We start with 0, because it is the first element. We find that the run of 0s is of length 2. This is the longest run so far. We proceed to the next element, 1, which has a run of three elements. This is longer than the zero run, so we store this as the longest run instead. The length of the 0s run is forgotten, as it is not needed. ... ... In the end, 5 is found to be the mode, as it has a run of 5. The trick is that finding the mode only requires that you keep track of the longest run SO FAR, while ignoring those runs shorter than the longest run found so far. After you've checked all the runs, the longest run so far is guaranteed to be your mode, because you've found the longest run in the whole array. Tip: you will only need a loop counter, two variables to keep track of the longest run found, and two more to keep track of the current run. You will only need to run through the whole array once. __________________ Code: #include <stdio.h> void J(chara){int* f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){ puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9 /33+f/39+f%3]==c\|\|a[i%9+f9]==c\|\|a[i-i%9+f]==c)goto* e;a[i]=c;J(a);a[i] ='0';e:;}}int main(int c,charv){int t=0;if(c>1){for(;v[1][ t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return** 1;}
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