Strange results when converting NSDate timeIntervalSinceReferenceDate to NSPoint
Strange results when converting NSDate timeIntervalSinceReferenceDate to NSPoint
- Subject: Strange results when converting NSDate timeIntervalSinceReferenceDate to NSPoint
- From: Gilles Celli <email@hidden>
- Date: Sat, 27 Jan 2007 13:47:03 +0100
Hi,
I need to convert NSDate to a meaningful NSPoint for the x-Axis of my
plotting application, so that the graph plots
the points to the corresponding time of the current day. The
application itself is a data acquisition app which acquires
every 0.5 seconds data from a digital Multimeter connected on the USB
port.
For Plotting / Graphing I'm using the excellent SM2DGraphView open-
source plotting framework:
http://developer.snowmintcs.com/frameworks/sm2dgraphview/
But I get strange results when converting NSDate
timeIntervalSinceReference to NSPoint.
Example:
[code]
------------------------------------------------------------------------
-----------------------------------------------------
NSPoint *graphData
for ( iRow = 0; iRow < curRow ; iRow++ )
{
// map the NSDate to a meaningful X co-ordinate.
graphData[iRow].x = [ k2700_str[iRow].acqDate
timeIntervalSinceReferenceDate ];
// Store the voltage value of the multimeter to
graphData[iRow].y = k2700_str[iRow].channel;
NSLog(@"acqDate as timeIntervalSRDate: %f | graphData.x = %f ",
[ k2700_str[iRow].acqDate
timeIntervalSinceReferenceDate ], graphData[iRow].x );
}
[/code]
------------------------------------------------------------------------
-----------------------------------------------------
[Result]
2007-01-26 18:09:30.599 AcquiKeithley[11852] acqDate as timeInterval:
191524170.000177 | graphData.x = 191524176.000000 =============>
different value !!!!
2007-01-26 18:09:30.600 AcquiKeithley[11852] acqDate as timeInterval:
191524170.500054 | graphData.x = 191524176.000000 =============>
different value !!!!
[Result]
So you see I get a different values. I tried to do a cast to (float)
but it didn't work.
I'm sure that I'm making something wrong.... :-(
Does anyone have any clues ?
Any help greatly appreciated. Thanks.
Gilles Celli
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