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Controling the color of line segments in a Log plot

  • To: mathgroup at smc.vnet.net
  • Subject: [mg90127] Controling the color of line segments in a Log plot
  • From: Donald DuBois <donabc at comcast.net>
  • Date: Mon, 30 Jun 2008 04:51:58 -0400 (EDT)

I would like to control the color of line segments in a Log plot. I have three Questions (A,B,C) regarding this problem.  

A simple example:  I start with the data yValues = Table[10^n, {n,10}] - which should also be the Y-axis tick values - and use ListLogPlot to graph it.

yValues = Table[10^n, {n, 10}]
xy = Transpose[{Range[Length[yValues]], yValues}]
ListLogPlot[xy, Joined -> True]


Question A . Does anyone find it peculiar that ListLogPlot seems to be taking 
Log to base 10 as a default as in the above plot when Log by itself defaults to base E?  This is FINE for me, as I want it to be to the base 10. But still, 
does anyone know why this is so or am I misconstruing something?


Question B. 
I would like to change the color to Red of the line segment with X values going from
3 to 6. (In general, I would like to change the segment color to Red for any number of segments of the same Log plot.) Is there a way to do this at the  ListLogPlot level (i.e.giving directives directly to ListLogPlot)?
That would be the simplest solution. 

I can change the color of this part of the graph by going down to the Graphics element level using Line as in the following, but this is tedious.

logY = Map[N[ Log[10, #]] &, yValues]
xyLog = Transpose[{Range[Length[logY]], logY}]
l2 = Graphics[{Red, Thick, Line[Take[xyLog, {3, 6}]]}];
l1 =  Graphics[{Line[Take[xyLog, {1, 3}]]}]; 
l3 =   Graphics[{Line[Take[xyLog, {6, 10}]]}];
Show[l1, l2, l3, Axes -> True, AxesOrigin -> {0, 0}]

Question C.  The above graph loses the original Y axis tick values which are contained in the yValues list defined above.  Is there any way to solve this?  I want the graph to look like the first graph above  with the same Y tick values (using ListLogPlot) except the Line segment with X values from 3 to 6 should be Red.

Thank you in advance for any help you can give me.

Don


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