[sharmilakumari]

I have a collection of 50000 points List<DataPoint> DataPoints;Each item in this collection contains (X,Y) co ordinates.These points have to be drawn using line and path in my line chart.Canvas size may vary.Drawing the entire collection will increase the load time.Hence I need to filter the points in such a way that I can get a sub collection of lesser number of points and this list will not affect shape of the chart to larger extent and also renders quickly.Suppose there are points like (1,2)(2,4)(3,6) which passes through same line.I can exclude(2,4).This method can be used as a first order filter.Can anyone please suggest or help me out with an algorithm how I can filter it further.Like excluding points which are very close to each other?

[digioz]

Originally Posted by sharmilakumari

I have a collection of 50000 points List<DataPoint> DataPoints;Each item in this collection contains (X,Y) co ordinates.These points have to be drawn using line and path in my line chart.Canvas size may vary.Drawing the entire collection will increase the load time.Hence I need to filter the points in such a way that I can get a sub collection of lesser number of points and this list will not affect shape of the chart to larger extent and also renders quickly.Suppose there are points like (1,2)(2,4)(3,6) which passes through same line.I can exclude(2,4).This method can be used as a first order filter.Can anyone please suggest or help me out with an algorithm how I can filter it further.Like excluding points which are very close to each other?

Have you considered using a Generic List instead of dataset? In most cases a Generic List would increase load speed by a factor of 50!

Pete

[m.timoney]

you can use trig to compare them

for example tan( (y[i+1]-y[i-1]) / (x[i+1]-x[i-1])) = tan( (y[i+1]-y[i]) / (x[i+1]-x[i]))
will tell you if the point at location i is in line with the one before and after (i think been a while since college trig classes)

add and error margin rather than a straight = and you can check for almost in the some line