Data labels above bars on grouped bar plot

I'm making a grouped bar plot (i.e., a bar plot with multiple bars in each category). I would like to add labels at the top of each bar to indicate its height. I was planning to just use the text function. However, bars within a given group all have the same x location (i.e get(h,'XData') is the same for all bar series). I'm not sure how to find the proper x location for each bar within a given group. Any ideas?

Thanks, Justin

[K E]

Matlab should offer bar labels as part of the bar function since bar plots are often presented this way. Really appreciate the workaround answers below though!

[dpb]

Submit the enhancement request to TMW @ www.mathworks.com

Answer 1

[dpb]

You're on the right track, the center of each group is at the axis tick value. For each bar in the group, use that value plus/minus a delta to locate the x position for your text.

I did an example of this for another poster within the last few weeks at most altho I don't have the link at hand. Perhaps a search will uncover it.

ADDENDUM:

OK, I looked at past answers--this one is pretty close altho I thought I did another. Maybe it was in the newsgroup instead...

http://www.mathworks.com/matlabcentral/answers/127300-draw-a-specialized-bar-graph#answer_134750

[Justin Solomon]

Thanks for your response. Do you know of a way to figure out what delta to use, other than just trial and error? i.e., is do you know how, given the xlimits and number of bars/group, to determine the exact position of each bar? The reason I ask is because I need my code to work for plots with varying sizes, aspect ratios, xlimits, etc so I don't want to have to trial and error for each condition.

[dpb]

The center is at the ticks and the width parameter controls what percentage of the difference is used. I've not tried to find a completely general formula, no.

I suspect if one were to read the bar source one could probably (at least eventually) decipher the algorithm used, but I've not done so.

ADDENDUM:

Well, I take that back -- the guts of the plotting is buried completely in the bowels of the HG object hierarchy and nothing is directly visible by the input X,Y values.

Think the only hope is to do some experiments and build an empirical adjustment correlation.

[Justin Solomon]

So I figured out a way to do this. I basically use the Xdata and Ydata properties of the underlying patch objects that are created when bar() is called. Thanks again for your comments. I appreciate it. Here's an example of some code:

Y=random('unif',0,100,[4 3]);
h=bar(Y);

ybuff=2;
for i=1:length(h)
    XDATA=get(get(h(i),'Children'),'XData');
    YDATA=get(get(h(i),'Children'),'YData');
    for j=1:size(XDATA,2)
        x=XDATA(1,j)+(XDATA(3,j)-XDATA(1,j))/2;
        y=YDATA(2,j)+ybuff;
        t=[num2str(YDATA(2,j),3) ,'%'];
        text(x,y,t,'Color','k','HorizontalAlignment','left','Rotation',90)
    end
end
ylim([0 100])

[dpb]

Good...I had thought would be able to find the computation of those in the code to save "handle diving" instead. Your way should work consistently; I'll stick a copy in my "bits 'n pieces" file (and then hopefully remember it's there next time :) ).

[Mostafa Darvishi]

Hello, I just tumbled into this post and I found it very interesting in my application. in this tripple bar plot, you used the array of [4 3] that means 4 intervals with 3 bars in each interval. But the function that you have used is a random number generator. My question is that how should I change the code in the case that I have 3 arrays as functions. For example I have three following arrays and I want to plot them in triple plot.

Y1 = [1 3 6 7 9 12 11]; Y2 = [12 5 8 13 11 1 4]; Y3 = [11 31 16 17 7 113 15];

[dpb]

Just past 'em together...

Y=[Y1;Y2;Y3].';  % create nx3 column array for *bar*

NB: The latest release of bar uses HG2 and returns a handle to a barobject, rather than the former bar series objects. This new object is essentially opaque to the the details and the data for the patches used to draw the bars isn't available from which to compute the individual bar positions so labelling bars as this example does won't work. I've not got a more recent version so not sure what the workaround is, if there is one or if one must resort back to the earlier "trick" I illustrated before.

Answer 2

[Will Adler]

This doesn't work in R2014b any more, due to this.

The available bar series properties no longer have the info for the location of the bar. Any idea how to recreate this in grouped bar plots?

[Kelly Kearney]

There's a hidden property called XOffset that can be used to find the bar positions:

Y=random('unif',0,100,[4 3]);
h=bar(Y);

yb = cat(1, h.YData);
xb = bsxfun(@plus, h(1).XData, [h.XOffset]');

hold on;
text(xb(:),yb(:), cellstr(num2str(Y(:))), 'rotation', 90);

[Efstathios Zavvos]

Thank you very much for your insight, it helped me solve the problem I had. This is not entirely correct, however, as it gets positions correctly but displays wrong values. The complete way to do it is:

Y=random('unif',0,100,[4 3]);
h=bar(Y);

yb = cat(1, h.YData); 
xb = bsxfun(@plus, h(1).XData, [h.XOffset]');

hold on;

for i = 1:size(yb,2)  
   for j = length(yb(:,1))

        text(xb(j, i),yb(j, i), cellstr(num2str(Y(i, j))), 'rotation', 90);

   end
end

[John Knag]

This is the best solution so far. Only problem is if you don't want to rotate your numbers 90 deg. They appear at the middle of each bar, so if you want them centered you have to put in a small offset the size of half of the text. I added an offset like this:

   xb = xb + (h(1).BarWidth*h(1).XOffset./((Y<100)+2))'

but that's not generalized, just works because my numbers were two or three digits.

[dpb]

Why doesn't 'horizontalalignment','center' work automagically? If they're centered correctly for the vertical orientation with the default horizontal position of 'left', seems like should be centered where you want them if don't rotate but use the alignment property.

I don't have recent release so can't test new HG...

[K E]

I believe the line should read

j = 1:length(yb(:,1))

and if you want horizontal not vertical alignment,

text(xb(j, i),yb(j, i), ...
sprintf('%.0f', Y(i,j)), ...
'clipping', 'off', ...
'horiz', 'center', 'vert', 'bot');

Thanks so much for this solution!

[dpb]

Query posted as Answer by Artem Smirnov moved here as comment by dpb--

"Is there any chance of putting labels inside the bars? That is a huge problem..."

[dpb]

What's the issue, specifically? The x-position for the text object to write is given by the above; simply modify the y-position to place where wanted in the bar instead above it--the y distances are computable directly from the data; don't need similar machinations as do for x.

I was thinking I'd seen additional properties mentioned that were useful having been introduced in HG2 but a search the other day didn't seem to find such, unfortunately, so guess I had mixed up with something else.

[Kelly Kearney]

Moving the labels inside the bars is a simple matter of changing the horizontal alignment so the right edge, rather than left, aligns with the bar height (and in most cases, adding a small offset to the y-position so the text doesn't sit flush to the bar edge).

This example also assumes that your bars are all large enough to fit the full text string.

Y=random('unif',30,100,[4 3]); % sample data
h=bar(Y);

yb = cat(1, h.YData);
xb = bsxfun(@plus, h(1).XData, [h.XOffset]');
hold on;
padval = 1;
htxt = text(xb(:),yb(:)-padval, cellstr(num2str(yb(:))), ...
    'rotation', 90, 'horiz', 'right');
set(htxt(1:3:end), 'color', 'w'); % for legibility

Answer 3

[Image Analyst]

For what it's worth, see attached demo. Adapt as needed.

[Justin Solomon]

Thanks for your comments. The difference in the case you show here and my case is that your bars are all centered on the ticks. If you have bar groups, then you have multiple bars grouped about the same xtick (see the image link in my original post). The only way I was able to figure out the exact center location of the each bar within a group was to get info from the underlying patch objects that are created when bar() is called. See my code above for an example.

Answer 4

[aliyar attaran]

for 2 bars one one y value:

for i2=1:numel(y)

    tx(i2,1)=text(x(i2),y(i2,1),num2str(y(i2,1),'%0.2f'),...
               'HorizontalAlignment','right',...
               'VerticalAlignment','bottom');
    tx(i2,2)=text(x(i2),y(i2,2),num2str(y(i2,2),'%0.2f'),...
               'HorizontalAlignment','left',...
               'VerticalAlignment','bottom');

end

Answer 5

[Elimelech Schreiber]

I've written a function to do just this. It's called barvalues, and is very easy yo use.

simply:

bar(x);
barvalues;

[dpb]

Nice start; unfortunately it still won't handle OP's problem with the grouped bar...consider

>> y = [2 2 3; 2 5 6; 2 8 9; 2 11 12];  % example from bar doc's...
>> bar(y)
>> barvalues
Error using axes
Invalid axes handle
Error in barvalues (line 49)
axes(ancestor(h,'axes')); % make intended axes curent. 
>>

Not yet general enough by default to handle the multiple handles...let's try using the figure handle...

>> barvalues(1,2)

Ah! Doesn't error, but returns the following figure--

where all the label are at the x-value of the centers of the groups instead on their respective bar centers.

In HG2(), there's a (hidden for heaven's sakes!!! :( ) property that can be queried to find where the bar centers are with respect to the tick values but you've got to know it exists before you'll ever be able to use it (a _*major_ foopah on TMW's part, this!)

>> hBar=bar(y);   % redraw, save handles this time...
>> get(hBar,'xoffset')
ans = 
    [-0.2222]
    [      0]
    [ 0.2222]
>> barvalues(hBar)
Error using axes
Invalid axes handle
Error in barvalues (line 49)
axes(ancestor(h,'axes')); % make intended axes curent. 
>>

Unfortunately, still doesn't know how to cope with the multiple handles.

It's not hard to make use of the above offset property to fixup the position; I posted an Answer/Comment not terribly long ago but can't find the link to it at the moment, unfortunately. It (at least comments that include it) was just in the last month or two at the latest.

ADDENDUM Found it; see following link...

<How-do-i-label-each-bar-in-bar-group-with-a-string-on-top>

It still should be part and parcel of the basic bar object as I commented therein.

(*) Prior to HG2, one could query the patch objects making up the bars properties and compute the mean of the x-positions, but TMW has made the bar object nearly opaque in HG2 so can't find those coordinates. At least there is the hidden property altho if it weren't for the likes of Yair it's unlikely anybody at all outside TMW would be aware of it.

[dpb]

I munged on your function some...haven't tested it thoroughly but it now works for the above case...haven't tried for more exotic examples. I know it won't work correctly for 'stacked' as the YData property isn't correct y location for it--not sure if it is retrievable or must be recomputed.

Modifications include

1. fixing up isaType to look at all objects in handle array rather than just one (this may be too simplistic in some cases, I don't know; didn't study the search logic enough to know if could possibly pass a group that might be other than bar handles)
2. using only one of the array handles in axes call to get axes handle (this could also possibly(?) be too simplistic if there are multiple bar objects but in multiple axes on a given figure), and
3. looping over the handle array and adding the .XOffSet property differential to the text call.

Doesn't seem an easy way to add updates at the Exchange so I'll just paste the modified routine here for your convenience...

[Giuseppe Naselli]

Thanks for the barvalues function Elimelech, very easy to use and solid

Very appreciated

G

Answer 6

[Halina H]

Hi , I would like to know how to code to get the total value of each bar in this grouped bar graph ie , total bincounts for the yellow bar, total bincounts for blue bar , and total bincounts for green bar. I am interested to know which of these 3 bars give the most information

[Image Analyst]

Since you plotted the 3 sets of data, you already have the counts. If you want the total number of counts, that's simply the number of elements in the data that you took the histogram of.