Fplot command only displaying a limited range. It displays [0,1] even though the range requested is [0,30].

Question

R ，2023-3-13

0
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Direct link to this question

https://ww2.mathworks.cn/matlabcentral/answers/1927950-fplot-command-only-displaying-a-limited-range-it-displays-0-1-even-though-the-range-requested-is

评论： Steven Lord ，2023-3-13

采纳的回答： Voss

The function I am using looks like this:

function va = genMotorVoltage(t)

if t < 10

va = 0.5*t;

elseif t >= 10 && t < 15

va = 5;

elseif t >= 15 && t < 25

va = -0.5*t + 12.5;

elseif t >= 25 && t < 25.5

va = 0;

else

va = NaN;

end

The script I use to test is just fplot(@genMotorVoltage, [0,30]);

It generates a plot that is [0,1]. It has the correct values for [0,10], which can only be found by scrolling. Then after [0,10], there is not graph, it simply ends.

It displays this error after scrolling:

> In defaulterrorcallback (line 12)

In matlab.graphics.interaction.validateAndSetLimits (line 28)

In matlab.graphics.interaction.uiaxes/InteractionStrategy/set2DLimits

In matlab.graphics.interaction.uiaxes/InteractionStrategy/setPanLimits

In matlab.graphics.interaction.uiaxes/DefaultAxesInteractionStrategy/setPanLimits

In matlab.graphics.interaction.uiaxes/InteractionStrategy/setUntransformedPanLimits

In matlab.graphics.interaction.uiaxes/DefaultAxesInteractionStrategy/setUntransformedPanLimits

In matlab.graphics.interaction.uiaxes/InteractionStrategy/setUntransformedPanLimitsInternal

In matlab.graphics.interaction.uiaxes/PanBase/move

In matlab.graphics.interaction.uiaxes/Drag/move_drag

In matlab.graphics.interaction.uiaxes.Drag>@(o,evd)hObj.move_drag(o,evd,customevd)

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Answer 1

Voss 2023-3-13

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1927950-fplot-command-only-displaying-a-limited-range-it-displays-0-1-even-though-the-range-requested-is#answer_1192145

fplot is sending a vector t to your function, not a scalar t. This causes an error if/when it gets to the first &&, which only happens if not all elements of t are less than 10 (i.e., the first if condition evaluates to false). So it runs ok if the xlimits are within [0 10] but beyond that you get an error.

Change your function to handle a vector t, for instance using logical indexing.

fplot(@genMotorVoltage, [0,30]);

function va = genMotorVoltage(t)

idx1 = t < 10;

idx2 = t >= 10 & t < 15;

idx3 = t >= 15 & t < 25;

idx4 = t >= 25 & t < 25.5;

va = NaN(size(t));

va(idx1) = 0.5*t(idx1);

va(idx2) = 5;

va(idx3) = -0.5*t(idx3) + 12.5;

va(idx4) = 0;

end

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Steven Lord 2023-3-13

I would suggest a slight modification to the index vectors. If you have a small number of possible intervals, indenting and using <= instead of >= would make the edges of the intervals clearer from the code.

t = 0:30;
    idx1 =           t < 10;
    idx2 = 10 <= t & t < 15; % t is in the interval [10, 15)
    idx3 = 15 <= t & t < 25;
    idx4 = 25 <= t & t < 25.5;

For a larger number of possible values I'd consider using the discretize function to identify into which interval each value of t falls.

bin = discretize(t, [-Inf 10 15 25 25.5])
bin = 1×31
   1     1     1     1     1     1     1     1     1     2     2     2     2     2     3     3     3     3     3     3     3     3     3     3     4   NaN   NaN   NaN   NaN
results = table(t.', bin.', VariableNames=["t", "bin"])
results = 31×2 table
tbin_____

   1 
   1 
   1 
   1 
   1 
   1 
   1 
   1 
   1 
   1 
   2 
   2 
   2 
   2 
   2 
   3 
tail(results) % Show the last couple values of t and bin
    t     bin
    __    ___

    3
    3
    4
  NaN
  NaN
  NaN
  NaN
  NaN