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digitalmars.D.learn - most elegant functional way to make a histogram

reply "Laeeth Isharc" <spamnolaeeth nospamlaeeth.com> writes:
I have four arrays of ints, each array representing a kind of 
event associated with that int (they all map to the same space).  
Each array might have the same number multiple times and each 
array will be of different length.

So I would like to plot the int line on x axis and show number of 
times that the number occurs for each array (4 bars for each int).

It's easy to do with loops, but what's best 
functional/algorithmic way, please?  Brain tired today.  I am 
trying to use these opportunities to learn the algorithmic way 
even if loop is more natural.

I could just make four new arrays of ints and use each instead of 
a loop.  Any better way?

Also, for bucketizing, any thoughts on best way to do using 
phobos?  (Cos probably I have too many ints and need to bracket 
them to plot a histogram).

Sorry if this is unclear.


Laeeth.
Aug 21 2015
next sibling parent reply "Laeeth Isharc" <spamnolaeeth nospamlaeeth.com> writes:
On Friday, 21 August 2015 at 20:09:22 UTC, Laeeth Isharc wrote:

 I have four arrays of ints, each array representing a kind of 
 event associated with that int (they all map to the same 
 space).  Each array might have the same number multiple times 
 and each array will be of different length.

 So I would like to plot the int line on x axis and show number 
 of times that the number occurs for each array (4 bars for each 
 int).

 It's easy to do with loops, but what's best 
 functional/algorithmic way, please?  Brain tired today.  I am 
 trying to use these opportunities to learn the algorithmic way 
 even if loop is more natural.

 I could just make four new arrays of ints and use each instead 
 of a loop.  Any better way?

 Also, for bucketizing, any thoughts on best way to do using 
 phobos?  (Cos probably I have too many ints and need to bracket 
 them to plot a histogram).

 Sorry if this is unclear.


I guess this kind of thing will do:
upRangeHighs.each!((ref a)=>(++histogram[a][0]));
Aug 21 2015
parent reply "yawniek" <dlang srtnwz.com> writes:
On Friday, 21 August 2015 at 21:08:25 UTC, Laeeth Isharc wrote:

 I guess this kind of thing will do:
 upRangeHighs.each!((ref a)=>(++histogram[a][0]));


    	

   int[] arr = [5,1,2,2,3,4,5,5,5];
   int[int] histo;
   arr.each!( a => ++histo[a]  );
   writeln(histo);

this works
Aug 24 2015
parent "Laeeth Isharc" <laeeth nospamlaeeth.com> writes:
On Monday, 24 August 2015 at 09:50:41 UTC, yawniek wrote:

 On Friday, 21 August 2015 at 21:08:25 UTC, Laeeth Isharc wrote:

 I guess this kind of thing will do:
 upRangeHighs.each!((ref a)=>(++histogram[a][0]));


    	

   int[] arr = [5,1,2,2,3,4,5,5,5];
   int[int] histo;
   arr.each!( a => ++histo[a]  );
   writeln(histo);

 this works


Thanks v much for suggestions, everyone.  In the end I just went 
with something like the above.
Aug 24 2015
prev sibling parent reply "BBasile" <bb.temp gmx.com> writes:
On Friday, 21 August 2015 at 20:09:22 UTC, Laeeth Isharc wrote:

 I have four arrays of ints, each array representing a kind of 
 event associated with that int (they all map to the same 
 space).  Each array might have the same number multiple times 
 and each array will be of different length.

 So I would like to plot the int line on x axis and show number 
 of times that the number occurs for each array (4 bars for each 
 int).

 It's easy to do with loops, but what's best 
 functional/algorithmic way, please?  Brain tired today.  I am 
 trying to use these opportunities to learn the algorithmic way 
 even if loop is more natural.

 I could just make four new arrays of ints and use each instead 
 of a loop.  Any better way?

 Also, for bucketizing, any thoughts on best way to do using 
 phobos?  (Cos probably I have too many ints and need to bracket 
 them to plot a histogram).

 Sorry if this is unclear.


 Laeeth.


loop-less approach, it consumes an InputRange in a recursive 
function.
Assuming histogramData is a custom InputRange:

---
void upperLevel()
{
     //histogramData = ...
     proc(histogramData);
     // continue once the range is consumed
}

void proc(ref histogramData)
{
     //something with front
     histogramData.popFront;
     if (!histogramData.empty)
         proc(histogramData);
}
---

I don't know if this approach can be used but this is an 
alternative to loops.
Not necessarily the best because local variables in proc() can 
lead to a stack overflow.
Aug 21 2015
parent "Meta" <jared771 gmail.com> writes:
On Saturday, 22 August 2015 at 02:12:41 UTC, BBasile wrote:

 On Friday, 21 August 2015 at 20:09:22 UTC, Laeeth Isharc wrote:

 I have four arrays of ints, each array representing a kind of 
 event associated with that int (they all map to the same 
 space).  Each array might have the same number multiple times 
 and each array will be of different length.

 So I would like to plot the int line on x axis and show number 
 of times that the number occurs for each array (4 bars for 
 each int).

 It's easy to do with loops, but what's best 
 functional/algorithmic way, please?  Brain tired today.  I am 
 trying to use these opportunities to learn the algorithmic way 
 even if loop is more natural.

 I could just make four new arrays of ints and use each instead 
 of a loop.  Any better way?

 Also, for bucketizing, any thoughts on best way to do using 
 phobos?  (Cos probably I have too many ints and need to 
 bracket them to plot a histogram).

 Sorry if this is unclear.


 Laeeth.


 loop-less approach, it consumes an InputRange in a recursive 
 function.
 Assuming histogramData is a custom InputRange:

 ---
 void upperLevel()
 {
     //histogramData = ...
     proc(histogramData);
     // continue once the range is consumed
 }

 void proc(ref histogramData)
 {
     //something with front
     histogramData.popFront;
     if (!histogramData.empty)
         proc(histogramData);
 }
 ---

 I don't know if this approach can be used but this is an 
 alternative to loops.
 Not necessarily the best because local variables in proc() can 
 lead to a stack overflow.


I believe in your example the compiler will perform TCO so you 
should be okay.
Aug 21 2015