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Re: Plotting points of the function at increments.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85733] Re: Plotting points of the function at increments.
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Wed, 20 Feb 2008 07:00:56 -0500 (EST)

On 2/19/08 at 7:03 AM, lrebanks at netvigator.com (Lea Rebanks) wrote:

>I am trying to plot the points of this function at increments of 1
>:-

>Plot[0.5x+5,{x,-5,5},PlotPoints*10]

The correct syntax for using PlotPoints would be:

Plot[0.5x+5,{x,-5,5},PlotPoints->10]

However, if you do

?PlotPoints

you will find this specifies the initial number of points for
Mathematica to sample your expression and does not do what you
seem to want.

>I wish to have an 'X' at each point on the line at f[1], f[2], f[3]
>. etc Hopefully I can adjust the size & colours of the 'X' markers
>aswell.

doing the following would work:

data = Table[{x, 0.5 x +5},{x,-5,5}];
ListPlot[data, Joined->True,
   Epilog->{Red,Text["X",#]&/@data}]

will plot the line y = 0.5 x + 5 with a red "X" at y[-1], y[-2]
etc. You can change the size by specifying the font size.
However, it would probably be simpler to adjust size if you were
to use a graphic primitive in place of a text character.

And if you wanted to restrict the "X" characters to appear only
in quadrant 1 (positive values) ListPlot code would become

ListPlot[data, Joined->True,
   Epilog->{Red,Text["X",#]&/@Cases[data, {_?Positive, _}]}]
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