Consulting waterfall chart matlab - matlab

Question

I was trying to create "consulting" waterfall chart in matlab, and I am having a really difficult time in creating it. I was expecting actually that there would be a built in way of doing that.
Given this data:
x = [5, 2, -5, 8, 2, 12];
total = [1, 0, 0 ,0 ,0, 1];
I want to make a waterfall chart.
Basically, the vector x has the values for the chart and the vector total indicates whether the corresponding column is a total column or not.
So the first column, is a 5 and is a total column. The second column is a two and it is not (so it adds up). The third column is minus five so it subtracts, and so on and so forth until the last column which is a total again. Below how the figure would look like.
1) How to get this figure?
2) How to color increases, decreases and totals with different colors?
3) How to include the connecting lines?

Answer 1

Method 1
Here's one possible solution using MATLAB's bar function.
Assumptions:
The total columns are always the first and last columns.
The basic idea is to use the 'Baseline' property of a Bar object, which allows a particular bar to start from a specific value. For example, bar([1,3,5], 'BaseValue', 2) produces 3 bars that start from the value 2: the first going down by 1 unit, the second going up by 1 unit, and the last going up by 3 units.
From testing on R2019b, unfortunately it appears that all Bar objects on an Axes must share the same BaseValue. Thus, for each Bar object to have its own Baseline value, each of them must be on a separate Axes object. We can workaround this by overlaying a bunch of Axes (one for each Bar) on top of each other, making all but one of them transparent. This way all bars will be visible.
Anyways, here's the function. The inputs are
ax (optional): a handle to an existing Axes object. You may want to do this if you have other things plotted already, or if you want to manually set various properties of an Axes.
y: a vector of all the incremental values. Note: the final value is NOT required, i.e. to reproduce the plot in the question, use y=[5, 2, -5, 8, 2];
The function outputs the handles to each Bar object created. You may want this to further change the EdgeColor of the Bars.
function h = wfall(ax, y)
if nargin == 1
y = ax;
ax = gca;
end
if ~strcmp(ax.NextPlot, 'add')
fprintf('hold on not set for current axes. Overriding.\n');
hold(ax, 'on');
end
y = y(:); % column vector
n = length(y);
cumy = cumsum(y);
set(ax, 'XLim', [0, n+1]+0.5, 'YLim', [min(min(cumy), 0), max(max(cumy), 0)]);
% colors:
% decrease - red - code as -1
% total - black - code as 0
% increase - blue - code as 1
set(ax, 'CLim', [-1, 1], 'ColorMap', [1 0 0; 0 0 0; 0 0 1]);
% copy a bunch of axes
for i = 1:n
ax(i+1) = copyobj(ax(1), ax(1).Parent);
end
% Make all subsequent axes invisible
% Make sure all axes will always be the same size by linking properties
set(ax(2:end), 'Color', 'none', 'XColor', 'none', 'YColor', 'none');
linkprop(ax, {'XLim', 'YLim', 'Position', 'DataAspectRatio'});
% define from/to of each bar (except 1st and last)
from = cumy(1:n-1);
to = cumy(2:n);
% color of each bar (except 1st and last)
c = double(y>0) - double(y<0);
c(1) = [];
% first total bar
h = bar(ax(1), 1, from(1), 'CData', 0, 'BaseValue', 0);
% 2nd to 2nd last bars
for i = 1:n-1
h(end+1) = bar(ax(i+1), i+1, to(i), 'CData', c(i), 'BaseValue', from(i), 'ShowBaseLine', 'off');
end
% last total bar
h(end+1) = bar(ax(1), n+1, cumy(n), 'CData', 0);
% setting FaceColor flat makes the Bars use the CData property
set(h, 'FaceColor', 'flat')
Run the code as follows to produce the following plot.
close all;
ax = gca;
h = wfall(ax, y(1:end-1));
Method 2
Here's another solution if you prefer not to stack Axes objects on top of each other.
In this case, we make an additional assumption:
The cumulative value is never negative (this would apply, for example, the cash in my pocket)
Simply, each bar we draw can be considered as one colored bar (either blue/red) that is partially covered by a shorter white bar.
function h = wfall2(ax, y)
if nargin == 1
y = ax;
ax = gca;
end
if ~strcmp(ax.NextPlot, 'add')
fprintf('hold on not set for current axes. Overriding.\n');
hold(ax, 'on');
end
y = y(:); % column vector
n = length(y);
cumy = cumsum(y);
from = cumy(1:n-1);
to = cumy(2:n);
% color values:
% 1 - blue (increase)
% 0 - white
% -1 - red (decrease)
c = double(y>0) - double(y<0);
c(1) = [];
upper = max(cumy(1:n-1), cumy(2:n));
lower = min(cumy(1:n-1), cumy(2:n));
h(1) = bar(ax, 2:n, upper, 'FaceColor', 'flat', 'CData', c);
h(2) = bar(ax, 2:n, lower, 'FaceColor', 'w');
h(3) = bar(ax, 1, cumy(1), 'FaceColor', 'k');
h(4) = bar(ax, n+1, cumy(n), 'FaceColor', 'k');
set(h, 'EdgeColor', 'none')
set(ax, 'CLim', [-1, 1], 'ColorMap', [1 0 0; 0 0 0; 0 0 1]);
Run the function as follows:
close all;
ax = gca;
h = wfall2(ax, y(1:end-1));
The resulting plot:
The result, however, is a bit ugly by my personal standards, since the white bar will partially cover the x-axis. You can fix this, however, by setting the lower YLim to a negative value, i.e. set(ax, 'YLim', [-0.5 inf])