@zenterix Did you notice that I specified the ytickmarks in the earlier listdensityplot example?

You can specify whatever you want for xtickmarks as well. Just for example,

     xtickmarks=[seq(100*i=100*(0.5+(i-1)*0.5),i=1..6)]

ps. I might not have made the following point clear enough before: I think that the idea of the convertArrayToTable procedure is poor. If your new data has the same kind of pattern (repeated blocks of indices in column 2, etc) then you could get rid of that procedure altogether. Using it is just asking for the kind of difficulties that you had earlier. For the earlier regular data you gave, it could be replaced just by this,   

read "./matrix.m":
m1 := Matrix(m1,datatype=float[8]):
MM:=`<|>`(seq(m1[1+120*(i-1)..120+120*(i-1),3],i=1..85)):

It's more robust as well as much terser. If your data is structured similarly then you could simply adjust for the new dimension sizes. I can't show you directly because you have not provided the new data.

@nm You are objecting to something about a case that you do not know for sure is in the domain that the OP is considering, and which can be handled trivially regardless.

But it might possibly be useful to the OP, so thanks.

More important IMO is that there is already a StringTools command to count the number of occurrences of a single character (ie. no need to write one's own), and that there is another existing command if one wants to tally all characters present.

@mmcdara The OP showed that it was interms of only volts in the Question, since the forced conversion to V^2 works.

@nm It's worth pointing out that evalc makes the assumption that the unknown names are real.

So, while this approach does attain the target it is unnecessarily confusing because it makes it appear that the transformation might depend on such properties or assumptions.

@Mike Mc Dermott There already is an option on the Tabulate command for specifying the relative widths of the columns. It's the weights option.

Combined with the options to specify the total width in either pixels or portion of the worksheet's width, that allows for complete specification of the column widths.

@nscheng There is no option to put the usual legend inside the plot's axes, no.

But you can fake it by adding a textplot and short section of similarly colored curve, etc.

@Thomas Dean I used ubuntu Linux.

Your original Question and the attached worksheet both contain no mention of using the maplet plot driver.

I answered that it worked for me before you mentioned the maplet plot driver.

note: This problem might be new in Maple 2022.

Here is another approach. It is simpler, more reliable, and more flexible.

It removes altogether the dubious mixture of turning the original data into a table and then hoping that densityplot will sample at exactly the right floating-point values.

restart;
currentdir(cat(kernelopts(homedir),"/mapleprimes")):

read "./matrix.m":
m1 := Matrix(m1,datatype=float[8]):

MM:=`<|>`(seq(m1[1+120*(i-1)..120+120*(i-1),3],i=1..85)):
V1:=m1[1..120,1]:
V2:=<seq(m1[1+120*(i-1),2],i=1..85)>:

F := Interpolation:-SplineInterpolation([V1,V2],MM,method=linear):
plots:-densityplot((x,y)->F(x,y), 1 .. 120, 0.9 .. 1.11,
                   colorstyle=HUE, style=surface);

If you want you could also add the grid=[121,86] option to densityplot. Since this is now interpolating, and no longer tied directly to the data values, you could also experiment with some other grid option values.

The above looks somewhat reasonably smooth. For other examples you might adjust some options to the Interpolate command (eg. cubic rather than linear, though slower).

You could also use that Matrix MM directly with the surfdata command, in the way I showed above. That is quite fast.

So it took a few moments to concoct a further adjustment to the original, using the same kind of approach.

Download table-hfloat_acc.mw

I'm not a fan of this particular densityplot approach -- and this might well end up being just as fragile.

@zenterix 

I suspect that the problem has something to do with how densityplot is constructing the x-y values. Any deviation in how it constructs, say, the y-values and you could get a slightly different value (float or HFloat, it hardly matters) and a mismatch with the indices of the inner tables. It seems like a fragile idea to try and match those values with more than one routine that splits the range. I think that I won't bother to try and further adjust that methodology.

Instead of relying of densityplot to get a precise match in the index values, you could turn the tables in T into Vectors, ie. turn all of T into a Matrix. In this way the actual indices are re-used to access the inner entries, with no mismatch.

You could then plot that Matrix using listdensityplot or surfdata.

Download table-hfloat_ac.mw
 

note: If the Matrix m1 has its entries arranged in an orderly fashion (ie. sorted wrt to both 1st and second columns -- I didn't bother to check) then the Matrix I used to plot could be constructed more directly, without need for all this table business. Or unprovided process which generates the m1 Matrix could be adjusted to construct the Matrix I used just above for plotting.

The Matrix MMM above, and Vectors of the common x- and y-values, could be used to build an interpolating procedure. That could be used to provide a smoother gradient of color. It could also be used with densityplot.

It works for me (not a blank plot), using Maple 2022.2.

Please don't put a close followup query on this topic in a wholly separate and new Question thread.

You could put it in a Reply here, or use the Branch button to connect them.

Your can zip up a .m file and then attach that in this forum.

@Rouben Rostamian  It's not a matter of Worksheet vs Document. It's a matter of the choice of input mode.

Inside text mode (after Crtl-t, say), one can direct enter the "approx" entry from the Common Symbols palette.

Inside text mode (after Crtl-t, say), one can also enter Ctrl-r and switch to 2D Math input mode, and then back to text if wanted. In Maple 2022 one may need to select the entered math use the right-click menu to convert to non-executable math, however.

Download text_math.mw

@Mikhail Drugov If you mouse-select and then do the right-click menu action,

   2D Math -> Convert To -> Atomic Variable

then afterwards you could use Maple's lprint command to see the underlying structure that is being pretty-printed.

Below we can see that in the case of the superscript the result is a Maple name (ie. surrounded by single left-ticks, also known as name quotes). The structure of the name looks similar to MathML.

Download msup.mw

Sometimes it's even convenient to use nprintf to programmatically construct the special name.

@Mikhail Drugov Here are three ways to get the * in the superscript without getting either single  left-ticks visible, or any parsing as conjugation, etc.

Note the the first way uses a methodology I mentioned in my earlier Answer.

misc_superscripts.mw