Standardising errorbar whiskers

Hi

I am using a set of data to construct a plot of errorbars with associated standard errors and whiskers for row=0:5;

for col = 0:2;

x=data(1+row,1+col);
y=data(1+row,4+col);
e=data(1+row,7+col);

if row==0;
    shape='sk';
elseif row==1;
    shape='dk';
elseif row==2;
    shape='^k';
end

subplot (3,1,1)
errorbar(x,y,e,shape, 'MarkerFaceColor','k','MarkerSize', 8, 'LineWidth',1),ylim ([0 1]),xlim ([0 3.5]);

hold on
box('off');

end

end

Unfortunately the whisker ends are not a uniform length. As can be seen in this example. I have added a highlight to emphasise what I am referring to.

http://dl.dropbox.com/u/3990478/errorbar_example.jpg

Either I would like to stop this increase happening or set the size of the whisker plot ends.

Please help (at the wits end with my whiskers)

Stephen

[Oleg Komarov]

We don't have data and row to run your example and from the code nothing abnormal should happen.

Answer 1

[Daniel Shub]

Is your xscale linear or log?

get(gca, 'xscale')

I have had problems with errorbar widths and log scales. If you are using a log scale, you could use

errorbar(log(x), ...

and a linear scale. The new numbers shouldn't be a problem since you are replacing the tick labels with text anyways.

Answer 2

[Stephen McKeever]

Hi

Daniel - I am not using a log scale.

I have removed the loop as suggest by another Matlab user. This worked well to a point. I have added some sample data to my DropBox to accompany the below function. http://db.tt/W6zhEA9

Cheers Stephen

function test_whiskers

load data

%This worked well
subplot (3,1,1)
hold on
h=errorbar(data(1:6,1)',data(1:6,4)',data(1:6,7)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','s')
h=errorbar(data(1:6,2)',data(1:6,5)',data(1:6,8)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','d')
h=errorbar(data(1:6,3)',data(1:6,6)',data(1:6,9)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','^')
text(-0.4,0.9,'a)','FontSize',12)

% For this plot though the whisker ends are quite large and I need the
% makers to be consistent with the groupings in graph a)
subplot (3,1,2)
hold on
h=errorbar(data(4,1:3)',data(4,4:6)',data(4,7:9)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','s')
text(-0.4,0.9,'b)','FontSize',12)

%So I tried separating the lines and changing the marker style but the
%whisker ends increase in size again
subplot (3,1,3)
hold on
h=errorbar(data(4,1)',data(4,4)',data(4,7)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','s')
h=errorbar(data(4,2)',data(4,5)',data(4,8)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','d')
h=errorbar(data(4,3)',data(4,6)',data(4,9)','k','MarkerFaceColor','k','MarkerSize',6, 'LineWidth',1,'linestyle','none'); ylim ([0 1]),xlim ([0 3.5]);
set(h(1),'marker','^')
text(-0.4,0.9,'c)','FontSize',12)

end

Answer 3

[Oleg Komarov]

The length of the horizontal line for the whiskers is proportional to [xdata(1) xdata(end)] the range on the x-axis.

In brief, if you have 5 points and their position on the x-axis is 1, 2, 3, 4, 5 the horizontal line will be proportional to 4.

You get different lengths because you plot several groups of points and the range is not assured to be constant.

There are two ways to get the same length for the horizontal line:

1. Force the range for each group to be constant by adding fake points to each group such that xdata(end) - xdata(1) = k. In order for these fake point to not appear on the graph, simply set some y-values out of the ylim
2. Modify manually the whiskers

To visualize the whiskers after you finished plotting one graph:

h = findall(gca,'Type','Line');
plot(get(h(2),'Xdata'),get(h(2),'Ydata'))

Good luck