simple scatterplot

[Manuel Valdes]

Hi Mike,

I hope that my eagerness to help wasn't in a way impolite. I am very grateful of all that I can learn every day from this forum, and this is one of the very rare cases where I thought I had some experiences to share. Specially, since like you, I used to program in TB. Anyway to trump Dave is absolutely out of my capabilities, and he is very, very hi in my regards.

The codes I posted can't deal with negative numbers, but that can be quite easily corrected. Please let me know if you have any other comment or question about it.

Best regards,

[Dave Biggs]

Hi Mike,
Hope your wife is coping OK?

I haven't made as much progress on the scaling / axes algo stuff as I would have liked yet. (I'm afraid I really don't deserve Manuel's high esteem ).

I did google my way to a site that discussed some possible solutions though and cobled together this test code. It shows some promise..

#COMPILE EXE
#DIM ALL
 
FUNCTION PBMAIN () AS LONG
 LOCAL xmin, xmax, xRange AS SINGLE
 LOCAL Steps AS LONG, StepSize AS SINGLE
  xmin = 1.4                  ' change to test
  xmax = 2.0                  '
  Steps = 10                 '
 
  xRange = xmax - xmin
  ? "xmin" xmin "xmax" xmax "xRange" xRange "Steps" Steps
  ' "Pretty step" algo
  CalculateStepSize(xRange, Steps) TO StepSize
  ?
  ? "StepSize" StepSize
  ' Adjust _min and _max
  xmin = StepSize * Int(xmin/StepSize)         ' -0.5 ?
  xmax = StepSize * ceil(xmax/StepSize)
  ? "Adjusted xmin" xmin "xmax" xmax
  ? "Actual steps " (xmax - xmin)/StepSize
 WAITKEY$
END FUNCTION
'------------------/PBMain
 
FUNCTION CalculateStepSize(Range AS SINGLE, Steps AS LONG) AS SINGLE
 LOCAL tempstep AS SINGLE
 LOCAL mag, magPow AS SINGLE, magMsd AS LONG
 
ReStart:
  ' calculate an initial guess at step size
  tempStep = range/Steps    : ? "tempstep" tempStep
  ' get the magnitude of the step size
  mag = FIX(LOG10(tempStep))  : ? "mag" mag
  magPow = 10^mag              : ? "magPow" magPow
  ' calculate most significant digit OF the NEW STEP SIZE
  magMsd = int((tempStep/magPow) + 0.5)  : ? "magMsd" magMsd
  ' promote the MSD TO either 1, 2, OR 5
    IF (magMsd > 5.0) THEN
      magMsd = 10.0
    ELSEIF (magMsd > 2.0) THEN
      magMsd = 5.0
    ELSEIF (magMsd > 1.0) THEN
      magMsd = 2.0
    END IF
  ? "magMsd*magPow" magMsd*magPow
   IF magMsd*magPow < 1 THEN Decr Steps : GOTO ReStart
 FUNCTION = magMsd*magPow
END FUNCTION
'------------------/CalculateStepSize

Perhaps a version of this method of might suffice to configure the two axes?

Give it a spin and see what you think.

[Manuel Valdes]

Hi Dave, Hi Mike,

Attached a simpler, bare-bones version, which I hope will respond in a better way to Mike's purposes.

The "POINTS.CSV" file was created with 100 pairs of values, using the RND function, except that I included three special point to control the accuracy of the deployment (-100,-100; 0,0 and 100,100).

I know this subject is in a way tricky, since I have been programming this type of stuff for the last 37 years.

Best regards,

[Dave Biggs]

Hi Manuel,

Thanks for the 'bare-bones' version I shall be picking over it for more goodies!

I've done a bit more with the CalculateStepSize function and incorporated it in this (final?) example.
It seems to work quite well with the data files in the zip below.
The sample data includes a modified version of your latest POINTS.CSV data. I removed the three special points and the function comes up with the same axes automagically!

[Manuel Valdes]

Hi Dave

Many thanks, now I have something good to study a fresh view of the subject. For starter I like the idea of the 0-0 axes, and I'm thinking whether to superimpose them using a different colour, or to start the grid lines from them going up and down, left and right.

As I am a lousy typist, I use this small code to produce my testing data files, playing with the random algorithm to get some effects:

 
#COMPILE EXE
'#DIM ALL
 
FUNCTION PBMAIN () AS LONG
 OPEN "POINTS.CSV" FOR OUTPUT AS #1
 PRINT #1, "X-Value,Y-Value"
 IV1&=15000
 IV2&=38
 FOR I%=1 TO 400
  PRINT #1,RND(-IV1&,IV1&)/100;CHR$(44);RND(-IV2&,IV2&)/100
  IV1&=IV1&-38
  IV2&=IV2&+38
 NEXT
 CLOSE 1
END FUNCTION

Best regards,

[Mike Hounsome]

Dave: GW Plot is just about exactly what I was trying to achieve - thanks, I've learned a lot. I'll be able to incorporate those ideas into my main program.

Manuel: Your program was too sophisticated for my simple needs for this particular job, but the ideas in it will be of great help to me when writing future programs. And I like your random data generator - most useful for testing. Is there any significance in the number 38?

Thanks again, guys.

[Manuel Valdes]

Hi Mike,

Good!. I'm also learning a lot from Dave's code. The number 38 doesn't have special meaning, except that it's 15000/400 rounded to the closest integer. The idea was to get the RND ranges closer and closer to 0, so as to concentrate the points around that value.

Best regards,