Adjusting plot fill to show two colours depending on overestima​​tion/unde​r​estimati​on

Hello,

I have the following code to plot my observed readings versus my modelled readings and the code works fine but does not clearly show regions where my modelled data is greater than observed data.

% Create figure
figure1 = figure;
XData = mod1_2001_2014(x,1)'; 
YData1 = mod1_2001_2014(x,5)'; 
YData2 = mod1_2001_2014(x,4)';
% Plot with fill
X = [XData fliplr(XData)];
Y = [YData1 fliplr(YData2)];
fill(X,Y,[0.678431391716003 0.921568632125854 1]);
ylim([0 max(YData2)+3])

I was wondering if there is a way to have this so that when the YData2 > YData1 the fill is red and when YData1 > YData2, the fill is the colour it is now.

Any ideas? Thank you!

Answer 1

[Thorsten]

Have a look at http://www.mathworks.com/matlabcentral/fileexchange/34876--greater-than--fill

or my solution that does need no interpolation but computes the intersection points.

function fillline(x, y1, y2, col1, col2) 
% Thorsten Hansen 2015-05-02 2014-11-27
% See also
% http://www.mathworks.com/matlabcentral/fileexchange/34876--greater-than--fill
if nargin < 3
  x = -10:10;
  y1 = sin(x);
  y2 = cos(x);
end
if nargin < 5
  col1 = [1 0 0];
  col2 = [0 0 1];
end

hold on
colpatch(y1 >= y2, col1, x, y1, y2)
colpatch(y2 >= y1, col2, x, y1, y2)
plot(x, y1, '-', 'Color', col1)
plot(x, y2, '-', 'Color', col2)
hold off

function colpatch(ind, col, x, y1, y2)

% special case 1: all values of y2 below y1: nothing to fill
if ~any(ind)
  return
end

% define fill color as a lighter version of the color on the line above
col = lighten(col);

% force row vectors for proper concatenation in fill below
x = x(:)'; y1 = y1(:)'; y2 = y2(:)'; ind = ind(:)';

% special case 2: no intersections, all values of y2 above y1
if all(ind)
  fill([x x(end) fliplr(x) x(1)], ...
       [y1 y1(end) fliplr(y2) y2(1)], col, 'EdgeColor', col);
  return
end

% general case: y1 and y2 intersect
val = cumsum(diff([0 ind]) == 1).*ind;
v = 1;
ind = find(val == v);
while ~isempty(ind)
  xi = x(ind); y1i = y1(ind); y2i = y2(ind); 

    % determine intersections to fill area between intersections
    % determine left intercept
    ii = ind(1);
    if ii > 1
      line1 = [x(ii) y1(ii); x(ii-1) y1(ii-1)];
      line2 = [x(ii) y2(ii); x(ii-1) y2(ii-1)];
      [xis_left yis_left] = lineintercept(line1, line2);
    else
      xis_left = [];
      yis_left = [];
    end
    % determine right intercept
    ii = ind(end);
    if ii < numel(x) 
      line1 = [x(ii) y1(ii); x(ii+1) y1(ii+1)];
      line2 = [x(ii) y2(ii); x(ii+1) y2(ii+1)];
      [xis_right yis_right] = lineintercept(line1, line2);
    else
      xis_right = [];
      yis_right = [];
    end

    % add patch
    fill([xis_left xi xis_right fliplr(xi)], ...
         [yis_left y1i yis_right fliplr(y2i)], col, 'EdgeColor', col);
    %set(h), pause
    v = v + 1; % next patch
    ind = find(val == v); % indices of next patch
  end

function [xis  yis] = lineintercept(line1, line2)
slope = @(line) (line(2,2) - line(1,2))/(line(2,1) - line(1,1));
m1 = slope(line1);
m2 = slope(line2);
intercept = @(line,m) line(1,2) - m*line(1,1);
b1 = intercept(line1,m1);
b2 = intercept(line2,m2);
% intersection
xis = (b2-b1)/(m1-m2);
yis = m1*xis + b1;
%plot(xis,yis,'ko','MarkerSize',10)

function col = lighten(col)
col = col + 0.8*([1 1 1] - col);

[mashtine]

Thank you Thorsten!

[mashtine]

Hey Thorsten,

I am trying to use your fillline function on my data (test, attached) and I cannot seem to get it to work. I keep getting this error when I enter

fillline(test(1:100,1),test(1:100,5),test(1:100,4));

Error:

Error using horzcat
Dimensions of matrices being concatenated are not consistent.

Error in fillline>colpatch (line 19)
val = cumsum(diff([0 ind]) == 1).*ind;

Error in fillline (line 14)
colpatch(y1 >= y2, col1, x, y1, y2)

Not sure why it is doing that as the horzcat should work. I removed all NaN's etc. Any ideas?

[Thorsten]

Hi Massao,

your data is a special case: there are no intersections, all values of y2 are above y2. If changed my fillline function above to handle this. Please do not hesitate to contact me if you find other cases where the functions does not work for you.

Best,

Thorsten

[mashtine]

Hi Thorsten,

Thanks again for this! Ran into another issue. When I reach to row 155 of my testdata (attached) the code goes wonky and I think it has to do with when y2 is greater than y1. It does not seem to be doing the switch even with both versions above. Unfortunately I am not too familiar with the colpatch function to figure it out myself.

[Thorsten]

Hi Masao,

I missed to also force "ind" to be a row vector. Please find the updated fillline function above. Hope this works now smoothly for everything :-)

Best,

Thorsten

[mashtine]

Thank you!

Answer 2

[Luuk van Oosten]

Dear Massao,

I do not know exactly how your data looks like, but you could use somthing like:

for i=1:lenght(yourdataset)
if YData1 < YData2 % Let matlab check if Ydata2 is larger than YData1
scatter( x(i,1), y(i,5), 15, [1 0 0], 'filled') hold on;
else % if this condition is not matched, then do the following:
scatter( x(i,1), y(i,4),15, [0 0.68 0.92], 'filled') hold on;
end

Have fun!

[mashtine]

Hi Luuk,

Unfortunately this is not what I want. I would like both y plot on one graph as lines with the space between them filled (as with my code above). I just want to adjust it so that regions where YData2 > YData1 the fill is red and when YData1 > YData2, the fill is the colour it is now. Attached is what I currently have but it shows the same colour during times when the lines criss-cross

[Luuk van Oosten]

Oops, excuse me. I'm not very familiar with plotting lines.

nevertheless, if you try something analogous to

if Ydata1 < Ydata2
   fill stuff in fancy blue
else
   fill stuff in red

I would expect that to work.

[mashtine]

Thanks Luuk but I am not sure how to do that will the flipr function