Hi,

You can create a circular (polar or radar) plot using a scattergraph chart
with polar coordinates. E.g. if a tachograph has 24 hours, each hour is 15
degrees. Initially it is easiest to have the clock start on the right (i.e.
where x=1, y=0 on an x,y graph) , so this would be midnight (0 degrees by
convention). The clock in this instance would go anti-clockwise from 0
degrees back to 0 (i.e. 360). E.g. 10 am would be 150 degrees (top-left
quadrant), noon would be 180 degrees (x= -1, y=0) etc. (The whole clock can
be transposed later to have midnight at the top (x=0, y=1) and clockwise
order).
Each point to be plotted on the tachograph has angle (time) and radial
distance from the centre of the plot (e.g. the speed at a particular time).
These are transformed into polar coordinates as follows:
x = radial distance from the centre * cos(angle in degrees * pi()/180) and
y = radial distance from the centre * sin(angle in degrees * pi()/180)

To plot the outer border to the clock, use a series of x,y coordinates from
0 to 360 degrees in steps of 15 degrees and constant radial distance.

HTH
Anthony

"olearyle" wrote:

How do I create a tachograph in Excel? I have been told that it is possible,
but it is called soething different!!