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Export the data file
![[Select 'cm A' and 'cm B' separately]](images/cm_selectv5.png)
You may contnue to analyse your data in Tracker, but if you want to
perform your data analysis using some other software, make
sure you export the data in text format: File ⇒ Export ⇒ Data File then
Save As...
The first three lines of the file (the header) should look like this:
cm_A
t x y
0.000000000E0 1.245986911E1 -1.328191643E1
3.200000000E-2 1.164289057E1 -1.262051106E1
...
Repeat for cm B. When reading these files into eXtrema, start on the third line: read cmA.dat\3 t,x,y
You can also select t,vx,vy if you prefer to let Tracker calculate
the velocities for you, in which case the file will look like this:
cm_A
t v_{x} v_{y}
0.000000000E0
3.200000000E-2 3.047083907E1 2.379658751E1
...
There will be two fewer points for velocities, as they are calculated as differences between
two xy-positions, so the end points will be missing. Start reading data on the fourth line:
read cmA.dat\4 t,vx,vy, and afterwards trim the last point from the t vector,
for which vx,vy values are missing: vector t len(t)-1
In Tracker v.6.x one can save data for multiple objects in a single data file by selecting them
in the Columns menu. The file may look like this:
#multi:
cm A cm B
t vx vy vx vy
0.032 30.47 23.79 -26.66 22.55
...
and a single command will suffice: read cmAB.dat\4 t,vxA,vyA,vxB,vyB
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