Error using Bar, X must be same Length as Y.

I am trying to plot on a bar chart through app designer and i'm getting the following error: Error using bar (line 172)

X must be same length as Y.

My code is as below:

bar(app.UIAxesPositionBar, T_BarChart.UndlyDate, T_BarChart{:,{'TotalPosition'}}, 0.8,'FaceAlpha',0.5);
hold(app.UIAxesPositionBar,'on');
bar(app.UIAxesPositionBar, T_BarChart.UndlyDate, T_BarChart{:,{'FuturesPosition','DeltaEquivPosition'}}, 0.8,'FaceAlpha', 0.5);

The second call to bar throws the error, when i inspect the table i'm using you can see its 1x4, the first call to bar works just fine.

You can see the table contents/variables below:

K>> bar(app.UIAxesPositionBar, T_BarChart.UndlyDate, T_BarChart{:,{'FuturesPosition','DeltaEquivPosition'}}, 0.8,'FaceAlpha', 0.5);
                

Error using bar (line 172)

X must be same length as Y.

K>> T_BarChart.UndlyDate

ans =

datetime

01-Dec-2019

K>> T_BarChart{:,{'FuturesPosition','DeltaEquivPosition'}}

ans =

1.0e+02 *

0 -1.887165000000000

K>> T_BarChart

T_BarChart =

1×4 table

UndlyDate FuturesPosition DeltaEquivPosition TotalPosition

___________ _______________ __________________ _____________

01-Dec-2019 0 -188.7165 -188.7165

Any ideas on why i am getting the "must be the same length" error?

[Nyaz Jamel]

 1500
Error using stem (line 43)
X must be same length as Y.

Error in untitled4 (line 6) stem(n,x) Please help My common:

n=input('input length of the sine seq'); L= input('up sampling factor'); fi= input('input signal freq'); t=0:n-1; x=sin(2*pi*fi*t); y=zeros(1,L*length(x)); y=x([1:L:length(x)]); subplot(2,1,1); stem(n,x) title('input sequence'); xlabel('time'); ylabel('amplitude'); subplot(2,1,2); stem(n,y(1:length(x))) title(['output sequence',num2str(L)]); xlabel('time'); ylabel('amplitude');

[Nyaz Jamel]

Help me bro

[Nyaz Jamel]

Note : Sample value=50, upsampling=2 input signal freq=1500

[Adam Danz]

With

stem(app.UIAxes, X, Y)

length(X) must equal length(Y). According to your error message, this is not the case for your values. It makes sense, right? X and Y are pairs of values so each X needs to have a Y value and vise versa.

Answer 1

[Adam Danz]

As the error indicates, x and y must be the same length. Here's a demo to understand the error:

bar(1,2)       % this is OK
bar([1,2,3],[1 1 1;2 2 2]) % this is also OK because
% length([1,2,3]) = 3 and length([1 1 1;2 2 2]) = 3

bar(1,[1,2])   % this produces an error
Error using bar (line 172)
X must be same length as Y. 

One solution is to specify two x values

bar([1,2], [4,5])

Another solution is to not specify the x values at all. It looks like one column is a single value while the other column might be two stacked values. In that case you can do something like this:

bar([0 5; 2 3],'stacked')

Read more about inputting matrices in bar(): https://www.mathworks.com/help/matlab/ref/bar.html

[Adam Danz]

(Replying to your "answers" which should be comments).

"What I'm looking for is to only have one side of the above graph only"

bar([1], [3],'FaceAlpha',.5)
hold on
bar([1;NaN], [1,2;NaN,NaN],'FaceAlpha',.5)
%       ^          ^   ^    Use padded NaN values
hold off

[Matt Glowacki]

This NaN solution works too, but I like the solution I used to add another row with 0 data better as it looks better with my app.

The answer regarding the 'stacked' chart was not really relevant, and the comment about not using x values did not work either.

Thanks for your help.

[Adam Danz]

Those suggestions were made prior to the example of your data you shared as an answer and that added further context.

Regarding the 0-padded table idea you're using, you mentioned "This doesnt look perfect as half the graph is blank, but its better than no graph". The NaN-padded table I suggested fixes this and does not result in half the graph being empty. If you'd rather use 0-padding, you can alway adjust the xlim of the graph.

[Matt Glowacki]

Thanks again for your help. Having that single row work for the bar graph was definitely what i was after initially, but after seeing how that looked in my app, which typically shows a 6+ month span, having the space was actually more visually appealing for my use.

[Adam Danz]

Glad I could help but congrats on finding a solution that works best with your data!

[Ulises Alejandro Aregueta Robles]

But then why this works with the example provided by MatLab documentation? (as below)

x = [1980 1990 2000];

y = [15 20 -5; 10 -17 21; -10 5 15];

bar(x,y,'stacked')

this is the example the matlab gives to plot stacked bars and here x is not the same length as y.

[Adam Danz]

x and y are the same length.

x = [1980 1990 2000];
y = [15 20 -5; 10 -17 21; -10 5 15];

>> length(x)
%ans =
%     3

>> length(y)
%ans =
 %    3

The length(x) function returns the length of the largest array dimension in X. In the data above, the size of x is 1x3 and the size of y is 3x3.

I updated my answer to provide an example of that, too.

Answer 2

[Matt Glowacki]

Thank you very much for your response! Perhaps I can provide a better illustration with this example code:

bar([1;2], [3;5],'FaceAlpha',.5)
hold on
bar([1;2], [1,2;3,2],'FaceAlpha',.5)
hold off

What I am trying to show is a total position and how the 2 pieces aggregate to that position. When my x variable has more than one value like above, my code works as I expect for each underlying date. What I'm looking for is to only have one side of the above graph only (like in my example above, my table only has one row, i want to add the first "total" bar, then just like the above code add the two bars on top of the first).

Is there another way to make sure that matlab knows that my code is passing 1 row with two variables in my original code above?

Thanks again for your help.

[Adam Danz]

Please reply in the comment section under my answer.

Answer 3

[Matt Glowacki]

So i was able to get mostly what I want by appending another row with 0's for each of the respective columns for one month after the single row in the table I was using. This doesnt look perfect as half the graph is blank, but its better than no graph. This is the table before and after modifying by the code below:

K>> T_BarChart
T_BarChart =
  1×4 table
     UndlyDate     FuturesPosition    DeltaEquivPosition    TotalPosition
    ___________    _______________    __________________    _____________
    01-Sep-2019           0                -305.428           -305.428   
K>> T_BarChart
T_BarChart =
  2×4 table
     UndlyDate     FuturesPosition    DeltaEquivPosition    TotalPosition
    ___________    _______________    __________________    _____________
    01-Sep-2019           0                -305.428           -305.428   
    01-Oct-2019           0                       0                  0   

dte = T_BarChart.UndlyDate(1);
T_BarChart = [T_BarChart; {datetime(year(dte),month(dte)+1,1),0,0,0}];
                
bar(app.UIAxesPositionBar, T_BarChart.UndlyDate, T_BarChart{:,{'TotalPosition'}}, 0.8,'FaceAlpha',0.5);
hold(app.UIAxesPositionBar,'on');
bar(app.UIAxesPositionBar, T_BarChart.UndlyDate, T_BarChart{:,{'FuturesPosition','DeltaEquivPosition'}}, 0.8,'FaceAlpha', 0.5);

[Adam Danz]

Please reply in the comment section under my answer.