Re: [ferret_users] Strange dots from VECTOR command

[Serena Illig <serena.illig.ird@xxxxxxxxx>]

Dear Ryo,

I have the same plot as you with pyferret v7.63 installed through miniconda. 

--> Note that there are no strange dots with old versions of Ferret (v6.71, v7.1 or v7.2) or even with Pyferret v7.62, all of them were installed from binaries.

Apparently, it has to do with the length of the arrow that is too small. If you plot a different region, a zoom, for instance, the scaling/length of the arrows will change, and the dots can disappear.

Check the result of:

use tmp.nc
shade/nokey 0*u_anom ! dummy
plot/vs/symbol/thick=1/size=0.5/color=red/nolabel/ov {38.25}, {143.58333333333333333333}

vector/aspect/ov/lenght=100 u_anom, v_anom

Apparently, when the length of the vector is too small, ferret and pyferret plot a dot symbol, but pyferret 7.63 keeps the size that you have defined previously with the command: plot/vs/symbol/thick=3/size=0.5/color=red/nolabel/ov  {38.25}, {143.58333333333333333333}

Check the result of

use tmp.nc

shade/nokey 0*u_anom ! dummy

plot/vs/symbol/thick=1/size=10/color=red/nolabel/ov   {38.25}, {143.58333333333333333333}

vector/aspect/ov u_anom, v_anom

The workaround could be to overlay a symbol with a reasonable size (/size=0.1) or to mask the data when the vector amplitude is "small":

let w_anom=(u_anom^2+v_anom^2)^.5

let mask=if w_anom gt 0.2 then 1 else 0

shade mask

plot/vs/symbol/thick=3/size=0.5/color=red/nolabel/ov  {38.25}, {143.58333333333333333333}

vector/aspect/ov u_anom/mask, v_anom/mask

I hope this helps,

Serena

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On Fri, Jul 29, 2022 at 7:02 PM Ryo Furue <furue@xxxxxxxxxx> wrote:

Dear Ferret users,

Has anybody seen this problem?  The VECTOR command plots some black dots as can be seen below. Run the attached Ferret script like so

pyferret -nodisplay -script try2.jnl

I also attach the datafile that the script uses.

These dots are very sensitive. If I change something, they are often gone but occasionally there are many more of them.  (That's why I couldn't simplify the problem further.)

macOS 12.4 & 12.5

PyFerret v7.63 (optimized); Darwin 19.6.0 - 10/13/20

Best regards,

Ryo

-----------

set data tmp.nc
shade/nokey 0*u_anom ! dummy
plot/vs/symbol/thick=3/size=0.5/color=red/nolabel/ov\
  {38.25}, {143.58333333333333333333}
vector/aspect/ov u_anom, v_anom
frame/file=tmp.png