real time plotting on iPhone using core plot?

Question

I want to use core-plot for drawing line graph dynamically. data won't come at a time, we will be receiving point by point dynamically.

Is it possible to draw the chart dynamically using core-plot i.e drawing point by point as on when we receive the (x,y) point?

Please help me, Thanks.

Condor

Hey Brad. Thanks for your comments. Could you please suggest a more recent tutorial ? Thanks in advance. – Djerba

Here is a tutorial (in french) but code is in english : geckogeek.fr/… – Mislike

Merci beaucoup, c'est encore plus simple comme ça :) – Djerba

Answer 1

Yes, you can do this reasonably easily. For each received data point, append it to an array of values to display. As these data points come in, call -reloadData on the Core Plot graph (or just the particular plot) to redraw the graph, passing in the array you just added a value to in response to the -numbersForPlot:field:recordIndexRange: delegate method.

If you need to adjust the plot range to track your data points (for a moving ticker), recalculate the new CPPlotRange for the X axis and set the plot space's xRange property to that.

Use the CPTestApp-iPhone, AAPLot, or StockPlot examples as templates for how to set up the line chart overall, and modify from that starting point.

I do something similar to this on the Mac in a scientific application:
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Whish

Thanks Brad. I would like to ask you one more help on this. How to implement the ZoomIn and ZoomOut for Core-plot? It would be great if you provide some example. Please help me. – Condor

@ram007: There is no native support for pinch-zooming at the moment. You could place the graph within a UIScrollView, and then rescale the graph extents in response to changes in the scroll view zoom scale, but that would also zoom the axes during a pinch event. Unfortunately, the best way would be to add this capability to the framework by modifying CPResponder to handle multitouch gestures, and that would take some work. – Whish

@BradLarson How do you do a live graph if you don't know that min and max to being with? How does the graph create the scale? – Dayflower

@Nic - You adjust the scale as needed when you add points. If you wish to maintain a fixed Y height, you can do that, or you can scale it based on new values that you've appended. Similarly, the X scale can move with your incoming samples. It's up to you to decide how to adjust the graph based on new data. – Whish

@BradLarson, how i received audio byte while audio file plying playing and depends on strength of sound i want to draw graph? – Pendulous

Answer 2

Sounds like you could make use of a demo project I put together and wrote about here (not core plot related though).

It draws a EKG graph but should easily be modified to use another input than the repeated "heart beat"...See line 320 in EAGLView.m where the indata is entered into the array.

Deformed