The Trendy application is being retired in the new year. The new web application, ThingSpeak, offers similar functionality. We recommend that active Trendy users who are looking to create new trends use ThingSpeak. To begin collecting your data in ThingSpeak, please read the tutorial : ThingSpeak for Trendy users. Although Trendy no longer allows the creation of new trends, the application will still remain accessible until January 13, 2016. Until that date, you can view your current trends and download your data. After that date, your data will no longer be accessible. Thanks for using Trendy and we encourage you to check out ThingSpeak.

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Plot for Number of Followers for MATLAB on Google+

This plot is broken.

Error using dateformverify (line 18)
DATESTR failed converting date number to date vector.  Date number out of range.

Error in datestr (line 195)
S = dateformverify(dtnumber, dateformstr, islocal);
  • Created by: Toshiaki Takeuchi
  • Latest result: Error using dateformverify (line 18) DATESTR failed converting date number to date vector. Date number out of range. Error in datestr (line 195) S = dateformverify(dtnumber, dateformstr, islocal);
  • Created on: 04 Feb 2012
  • Liked: 7 times

This plot shows the growth of followers for MATLAB page on Google+. It then fits a linear trend line and predicts the number of the followers on the next day.

Since the plot is just a PNG image file and it gets updated automatically on a daily basis, you can embed the plot on your blog or wiki by using HTML img tag. i.e.<img src="http://www.mathworks.com/matlabcentral/trendy/images/plots/plot_706.png">

Give it a try!

Plot Image
% time1493 and data1493 available for use
% for MATLAB news on Google+ from Topsy
% 
% This plot shows the growth of followers for MATLAB page on Google+. 
% It then fits a linear trend line and predicts the number of the followers on the next day.
% Since the plot is just a PNG image file and it gets updated automatically on a daily basis, you can embed the plot on your blog or wiki by using HTML img tag.
% Give it a try!

% Number of Followers for MATLAB on Google+
%   time vector is: time1305
%   data vector is: data1305

% Starting date for prediction
% t0 = datenum('22-Feb-2012');
% keep = time1305 >= t0;
% 
% tm = time1305(keep);
% dm = data1305(keep);

tm = time1305(:)';
dm = data1305(:)';

% Fit MATLAB Follower growth
[p,S,mu] = polyfit(tm,dm,1);
p1 = [p(1)/mu(2) p(2)-p(1)*mu(1)/mu(2)];

% Project into the future
tf = [tm tm(end)+1];
df = polyval(p1,tf);

% Predict the number for the next day
d=round(df(end));
t=datestr(tm(end)+1,1);
next=sprintf('Prediction for %s: %d followers',t,d);

% Predict when it will reach a goal
goal = 1500;
g = sprintf('Will reach %d followers on ', goal);
reach = [g datestr((goal - p1(2))/p1(1),1)];

% Was previous prediction correct?
[p,S,mu] = polyfit(tm(1:end-1),dm(1:end-1),1);
p2 = [p(1)/mu(2) p(2)-p(1)*mu(1)/mu(2)];
prev = polyval(p2,tm(end-1)+1);
prev = round(prev);
gap = prev-dm(end);
t=datestr(tm(end),1);
prevp=sprintf('Prev Prediction for %s off by %d',t,gap);

% trend up to the shift
% tn = time1305(~keep);
% dn = data1305(~keep);
% [p,S,mu] = polyfit(tn,dn,1);
% p3 = [p(1)/mu(2) p(2)-p(1)*mu(1)/mu(2)];
% tf = [tn tf];
% df = [polyval(p3,tn) df];

% Plot the data and trend
% subplot(2,1,1)
  plot(time1305,data1305, '-');
  hold on
  line(tf,df,'Color','magenta','LineStyle','-')
  plot(tm(end),prev, 'ro');
  hold off
  datetick
  title('Number of Followers for MATLAB page on Google+')
  legend('Followers','Trend','Prev Prediction', 'Location', 'Best')

  % Get normalized position for annotation
  yrange = ylim;
  ymin = yrange(1);
  ymax = yrange(2);
  YPos1 = ymin+0.95*(ymax-ymin);
  YPos2 = ymin+0.90*(ymax-ymin);
  YPos3 = ymin+0.85*(ymax-ymin);

  % Add the predictions
  text(time1305(1),YPos1,next)
  text(time1305(1),YPos2,prevp)
  text(time1305(1),YPos3,reach)

%  subplot(2,1,2)
%    gap = length(time1305)-length(time1493)
%    padding=repmat([NaN],1,gap);
%    plot([time1305(1:gap) time1493], ...
%      [padding data1493], 'o-');
%    datetick
%  title('MATLAB mentions on Google+ per Topsy')
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