[proFit-list] Finding the min or max of data

[Davide Guarisco]

Then you have never dealt with large amount of data. I do, and I can assure you that pro Fit takes an awfully long time to sort a substantial data file (when it doesn't hang). 

But I happen to have a fondness for good and efficient programming, and sorting really isn't the way to solve this problem. The best sorting algorithms behave as O(n log n), whereas this problem can be solved in O(n). 


Consider this simple code:

procedure findminmax(var xmin,xmax: extended;var imin,imax: integer);
{Finds the minimum (xmin), maximum (xmax) values and their indices of the Y column of the current data window}
var ymin,ymax,yx: extended;
    i: integer; 
    
begin
	ymin:=InvalidNum;
	ymax:=InvalidNum;
	imin:=InvalidNum;
	imax:=InvalidNum;
   	{Find first valid data}
	for i:=1 to NrRows do
		if not(invalid(data[i,YColumn])) then
			begin
				ymin:=data[i,YColumn];
				ymax:=ymin;
				imin:=i;
				imax:=imin;
				Leave;
			end;
   for i:=i+1 to NrRows do
      begin
         if not(invalid(data[i,YColumn])) then
         begin
         yx:=data[i,YColumn];
         if yx>ymax then 
            begin
               ymax:=yx;
               imax:=i
            end
         else
            if yx<ymin then
               begin
                  ymin:=yx;
                  imin:=i
               end;
         end;
      end;
   xmin:=ymin;
   xmax:=ymax
end; {findminmax}

I think this does what the OP asked for. 

Davide




On May 9, 2013, at 8:19 AM, Camaioni, Donald M wrote:

> Hi Davide,
> 
> It can be programmed via a single command using pro Fit's built in sort routine, e.g., in pro Fit's Pascal programming language:
> 
> Sort(window , referenceCol , order , selectionOnly );
> 
> Efficiency of this routine has never been an issue for me.
> 
> Don
> 
> On May 9, 2013, at 7:44 AM, Davide Guarisco wrote:
> 
> I would advise against doing that. Sorting is extremely inefficient.
> 
>     Davide
> 
> 
> 
> 
> 
> On May 8, 2013, at 7:15 AM, Camaioni, Donald M wrote:
> 
> I am thinking you would just sort the data and read values from either the resulting first or last row. -Don
> 
> On May 8, 2013, at 6:54 AM, Dave wrote:
> 
> Hi folks,
> 
> While I am anxiously awaiting the Cocoa based, Retina- ready version of pro Fit, a question:
> 
> Is there an easy way to find the local minima/ maxima of a set of data or selection of data, and report that point? I mean finding the max or min y value and reporting the x,y coördinate.
> 
> Thanks,
> Dave
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> ––––––––––––––––––––––––––––––––
> Donald Camaioni, PhD
> Staff Scientist
> Catalysis Science Group
> PHYSICAL SCIENCES DIVISION
> 
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      Davide
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Davide Guarisco
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