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Re: [ferret_users] wind stick plot



Hi Thuckan,

| Dear Ferreters,I am trying to represent wind velocity and direction
| in the same plot using stick plot.I could do it with a data set
| having u and v components of wind-see windstick_ferret.gif. I
| presume that the length of the stick is proportional to the wind
| speed sqrt(u^2+v^2) and the direction of the stick indicates the
| direction to which wind is blowing. But I don't understand why the
| Y-axis shows postive as well as negative values, where as wind speed
| should be always positive.

A stick plot is a plot on the u-v plane.  Suppose you have a time
series of a vector (u(t), v(t)).  Then, you plot line segments

  from (c*t, 0) to (c*t+u(t), v(t))

on the u-v plane for all values of t, where c is an arbitrary
constant.  Each line segment represents the vector (u(t), v(t))
but its origin is shifted as (c*t, 0).

So, the vertical axis is v and the horizontal axis is u.
But, the horizontal axis is "labeled" with time t, just for
convenience, to represent the shift of the origin (c*t,0).

Does this answer your first question?

I'll leave the remaining questions out.  I haven't looked
at your journal file.

Regards,
Ryo


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