# How Long Until There Are 25,000 Files on the File Exchange?

• Created by: Ned Gulley

### Ned Gulley (view profile)

• Latest result: Plot created
• Created on: 23 Jan 2012
• Liked: 3 times

Also calculate the rate at which it's growing.

```% Files on the File Exchange
%   time vector is: time1151
%   data vector is: data1151

data1151 = data1151(:);

% Pick N days worth of data
N = 90;
t0 = now - N;
% Goal in thousands
goal = 25;
pick = time1151 > t0;
t = time1151(pick);
d = data1151(pick)/1000;

plot(t,d,'b')
[p,S,mu] = polyfit(t,d,1);

% p1 is the equation for the linear fit to the data
p1 = [p(1)/mu(2) p(2)-p(1)*mu(1)/mu(2)];
% p2 is the equation for the target amount
p2 = [0 goal];

% ti = t_intersect, di = d_intersect
ti = (p2(2) - p1(2))/(p1(1)-p2(1));
di = p1(1)*ti + p1(2);

tf = [t0 ti+1];
df = polyval(p1,tf);

line(tf,df,'Color','red','LineStyle',':')
line([t0 ti+1],goal*[1 1],'Color','black')
line(ti,di,'Marker','o','Color','red')

set(gca,'FontSize',16)
datetick

title(sprintf('The File Exchange is growing by %4.1f files/day', 1000*p1(1)))
xlabel(sprintf('%d,000 files on %s',goal,datestr(ti)))
ylabel('Number of Files (1000s)')```
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