LogLogPlot for negative values

Questions
1

Hi everyone,
I have tried to plot a function with negative values using LogLogPlot but I could not.
Please, could you help me with this problem?
Please see my attempt attached.

Kind regards
Omar

LogLogPlot.nb (46.2 KB)

2

If a is negative and real, then Log [ a ] = I Pi + Log[ Abs[a] ]. ( I^2 = -1 )

This is a complex number with constant imaginary part. So you might want to consider

LogPlot[Abs[\[Omega]1] /. qx -> 1000, {El, 10^-6, 2.52  10^9}, 
 Frame -> True, FrameLabel -> {"\!\(\*
StyleBox[\"E\",\nFontSlant->\"Italic\",\nFontColor->GrayLevel[0]]\)", 
   "\!\(\*
StyleBox[SubscriptBox[\"\[Omega]\", \"+\"],\nFontSize->14,\n\
FontWeight->\"Bold\"]\)"},
 PlotStyle -> Black, FrameTicksStyle -> Directive[Black, 9],
 PlotRange -> Full, ImageSize -> 650]

or, perhaps better

Plot[Log[Abs[\[Omega]1]] /. qx -> 1000, {El, 10^-6, 2.52  10^9}, 
 Frame -> True, FrameLabel -> {"\!\(\*
StyleBox[\"E\",\nFontSlant->\"Italic\",\nFontColor->GrayLevel[0]]\)", 
   "\!\(\*
StyleBox[SubscriptBox[\"\[Omega]\", \"+\"],\nFontSize->14,\n\
FontWeight->\"Bold\"]\)"},
 PlotStyle -> Black, FrameTicksStyle -> Directive[Black, 9],
 PlotRange -> Full, ImageSize -> 650]
3

Hi Omar,

In addition to Hans’s answer, take a look at ReImPlot and AbsArgPlot which were introduced in version 12.

4

Thanks Hans for your for your help.

Should I use this code which is similar to the original one?

Plot[-Log[Abs[[Omega]1]] /. qx → 1000, {El, 10^-6, 2.52 10^9},
Frame → True, FrameLabel → {“!(*
StyleBox["E",\nFontSlant->"Italic",\nFontColor->GrayLevel[0]])”,
“!(*
StyleBox[SubscriptBox["[Omega]", "+"],\nFontSize->14,\n
FontWeight->"Bold"])”},
PlotStyle → Black, FrameTicksStyle → Directive[Black, 9],
PlotRange → Full, ImageSize → 650]

Kind regards
Omar

5

Thanks a lot, Rohit.

Kind regards
Omar

6

Well, Omar, frankly spoken I don’t know.
What do you want to achieve with this plot?
Show what?
Do you want to have this plot for a publication?
If so, what is your reasoning with regard to the plot?