Wolfram Mathematica

Wolfram Blog: Analyzing the Impact of Political Messages with the Wolfram Language

2:55 PM

ClearAll["Global`*"]
par = {1, 5, 10, 25};
ron = 50 10^-3;
iLoad = 1;
(*Proposed Vestigial Conduction Loss 2*)
pLossProposedGen2[iLoad_, dcr_, ron_, m_, n_] :=
iLoad^2 (dcr + ((m^2 + 2 n - m (1 + n)) ron)/(-1 + m + n));
(*Conventional Buck-Boost Conduction Loss*)
pLossConBB[iLoad_, dcr_, ron_] := iLoad^2 (2 ron + dcr);
Block[{t =
Table[{pLossProposedGen2[iLoad, dcr, ron, m, n]/
pLossConBB[iLoad, dcr, ron]}, {dcr, par*ron}]},
Manipulate[
Plot[Table[{pLossProposedGen2[iLoad, dcr, ron, m, n]/
pLossConBB[iLoad, dcr, ron]}, {dcr, par*ron}], {m, 0, 1},

Can anyone tell me why only one legend is plotted?

Feeds

3:54 PM

posted on December 10, 2019 by Jon McLoone

Much effort and money are spent trying to analyze whether political messages resonate with the electorate. With the UK in its final days before a general election, I thought I would see if I could gain such insight with minimal effort. My approach is simple: track the sentiment of tweets that mention each party. Since [...]

Q: Plot draws list of curves in same color when not using Evaluate

4:44 PM

@anhnha See this question:

This example comes from the Mathematica documentation for Plot under Basic Examples. Can someone please explain why these are each plotted as a different color in this case: Plot[Evaluate[Table[BesselJ[n, x], {n, 4}]], {x, 0, 10}, Filling -> Axis] But when Evaluate[] is removed, all of them...

@LukasLang I read that before.
In my case, the legend works well without Manipulate

The problem only happens when Manipulate is added.

but you're right

it works with Evaluate

I need to see the code again

it's too complex so I lost track

@LukasLang I think I know why it works without Manipulate. It's because I set the expression to t and use the variable t.
I tried to use t in the plot but it didn't work. Do you know why?

@anhnha Can you show the exact code you're using without Manipulate?

@LukasLang I posted all above

I misread

one minute

ClearAll["Global`*"]
par = {1, 5, 10, 25};
ron = 50 10^-3;
iLoad = 1;
(*Proposed Vestigial Conduction Loss 2*)
pLossProposedGen2[iLoad_, dcr_, ron_, m_, n_] :=
iLoad^2 (dcr + ((m^2 + 2 n - m (1 + n)) ron)/(-1 + m + n));
(*Conventional Buck-Boost Conduction Loss*)
pLossConBB[iLoad_, dcr_, ron_] := iLoad^2 (2 ron + dcr);
Block[{t =
Table[{pLossProposedGen2[iLoad, dcr, ron, m, 1]/
pLossConBB[iLoad, dcr, ron]}, {dcr, par*ron}]},
Plot[t, {m, 0, 1},
PlotStyle -> {Directive[Blue, Thick], Red, Darker@Green,

@LukasLang

I use n = 1 for that case

5:13 PM

@anhnha if you wrap the Block in Manipulate I see no issues. I varied your n parameter like:

Manipulate[
 Block[....],
 {n, 1, 10}
  ]

And it seemed fine

@b3m2a1 yes, it works. I didn't know you can put Block inside Manipulate like that

@anhnha You can put whatever you want inside Manipulate

It doesn't care

5:31 PM

@anhnha It works with Block because Plot has special handling for a single symbol in the first argument implemented. So since Plot sees t as the first argument, it decides to evaluate it to see how many functions it need to plot. If it sees Table[…] on the other hand, it sees only a single thing, and thus decides it only needs one color.

@anhnha @LukasLang ahh I thought the issue was with the legend on the right

Apparently it's the classic "needs an Evaluate" issue

yes, indeed - I just got a bit confused by the Block[{t = …}, Plot[t, …]] example... As far as I knew, that shouldn't have worked. It seems you can never be certain with stuff like this until you try it ;)

Initially I use t inside the Plot function. I also put Manipulate inside Block.

However, the variable t inside Plot turned red

so I copy and paste the whole expression instead of t

that's where the problem happened

@LukasLang Plot isn't going to relocalize the t unless you use it as the plotting variable

@anhnha fundamentally the problem was that you needed to use Evalute@Table[...], though

Otherwise Plot doesn't know how many functions you're trying to plot and so miscolors them and mislabels them in the legend

ClearAll["Global`*"]
par = {1, 5, 10, 25};
ron = 50 10^-3;
iLoad = 1;
(*Proposed Vestigial Conduction Loss 2*)
pLossProposedGen2[iLoad_, dcr_, ron_, m_, n_] :=
iLoad^2 (dcr + ((m^2 + 2 n - m (1 + n)) ron)/(-1 + m + n));
(*Conventional Buck-Boost Conduction Loss*)
pLossConBB[iLoad_, dcr_, ron_] := iLoad^2 (2 ron + dcr);
Block[{t =
Table[{pLossProposedGen2[iLoad, dcr, ron, m, n]/
pLossConBB[iLoad, dcr, ron]}, {dcr, par*ron}]},
Manipulate[
Plot[t, {m, 0, 1},
PlotStyle -> {Directive[Blue, Thick], Red, Darker@Green,

Can you explain why this doesn't work?

The variable t turns red

5:47 PM

You have the order wrong

Block localizes t

Manipulate only has an effect outside of the scope of the localization

Mathematica is telling you that you messed up the ordering

If you need to localize a variable, you want to do it inside Manipulate

Another way you could have written that to take effect of the localization that Manipulate does:

Manipulate[
 t = Table[{pLossProposedGen2[iLoad, dcr, ron, m, n]/
     pLossConBB[iLoad, dcr, ron]}, {dcr, par*ron}];
 Plot[t, {m, 0, 1},
  PlotStyle -> {Directive[Blue, Thick], Red, Darker@Green,
    Directive[Orange, Thick]}, PlotLegends -> (Row[{"DCR", #}] & /@ par),
  AxesLabel -> {Style["M", 16, Bold], Style["P", 16, Bold]},
  GridLinesStyle -> LightGray, PlotRange -> {0, 1.8}, AxesOrigin -> {0, 0},
  Ticks -> {Automatic, Range[0.6, 1.8, 0.2]},
  GridLines -> {Automatic, Range[0.6, 1.8, 0.2]},

Notice the {t, None} at the end. That means: "treat t as local, but don't give it a valuate"`

@b3m2a1 Yes, Plot will not relocalize t. But I expected Plot to use the same color for all curves in that case nevertheless, similar to how it does in the Table case. Compare:

t = Table[x^i, {i, 3}];
Plot[t, {x, 0, 1}]
Plot[Table[x^i, {i, 3}], {x, 0, 1}]
Plot[{x, x^2, x^3}, {x, 0, 1}]

Ah I see what you mean

(The first one is news to me, the others are expected)

Yeah that's clearly a special case since people probably use it so often

Using {t, None} looks neat

"Block localizes t
Manipulate only has an effect outside of the scope of the localization"

I put Manipulate outside of the scope.

Block[{t=..},

Manipulate[Plot[t,..], {n,1,5,1}]]