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Re: [ferret_users] multiple slabs, definition of the one-point axis, and precision.


That's an interesting detail. You're right - the regridding operation here does require us to use @NRST to ensure the right result. I'll add this to the documentation.


On 11/21/2017 6:41 PM, Ryo Furue wrote:
Hi Ansley,

Thanks for your answer!  but, my point was different.

DEFINE AXIS/Z/UNITS=meters/DEPTH zaxis = {0,10,20,50,100}

DEF GRID/Z=zaxis uv_grid

let zz = z[gz=zaxis]

let zval = zz[k=1]
DEF AXIS/Z=`zval`:`zval`:1 zaxis1
My point was that this (the above line) can be problematic.  How many digits do we need for `zval` ?

The following line
LET/TITLE="My U data" u1 = u[G=uv_grid]
will give an undefined layer if the sole gridpoint of zaxis1 doesn't match any of the z-coordinate values of uv_grid .  Interpolation doesn't happen because zaxis1 has only one gridpoint.

The workaround I found was to use G=uv_grid@NRST .

The example in the user's guide works because the z-coordinate values are whole numbers.

So I thought it would be useful if we can directly get the internal value of a variable without first producing a text representation of it by the backquote `_expression_`.



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