<div dir="ltr"><div class="gmail_default" style="font-size:small">Hi folks,</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style="font-size:small">Just a minor correction here. Since this is WRF data, we have specific functions for extracting the index locations of a grid given lat/lon values. See "wrf_user_ll_to_ij":</div><div class="gmail_default" style="font-size:small"><br></div><div class="gmail_default" style=""><a href="http://www.ncl.ucar.edu/Document/Functions/WRF_arw/wrf_user_ll_to_ij.shtml">http://www.ncl.ucar.edu/Document/Functions/WRF_arw/wrf_user_ll_to_ij.shtml<br></a></div><div class="gmail_default" style=""><br></div><div class="gmail_default" style="">This is similar to closest_val, except you give both lon, lat points (in that order) and it gives you the i,j index values back in one call.</div><div class="gmail_default" style=""><br></div><div class="gmail_default" style="">You can see a graphical example of this function at:</div><div class="gmail_default" style=""><br></div><div class="gmail_default" style=""><a href="http://www.ncl.ucar.edu/Applications/wrfdebug.shtml">http://www.ncl.ucar.edu/Applications/wrfdebug.shtml<br></a></div><div class="gmail_default" style=""><br></div><div class="gmail_default" style="">(example wrf_debug_4.ncl)</div><div class="gmail_default" style=""><br></div><div class="gmail_default" style="">Good luck,</div><div class="gmail_default" style=""><br></div><div class="gmail_default" style="">--Mary</div><div class="gmail_default" style=""><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jan 26, 2016 at 7:47 AM, Karin Meier-Fleischer <span dir="ltr"><<a href="mailto:meier-fleischer@dkrz.de" target="_blank">meier-fleischer@dkrz.de</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Sorry, little mistake in coloring the lines. It must be:<div><div class="h5"><br>
<br>
<tt> <font color="#3333ff"><b>lat13</b></font> =
closest_val(13,lat)</tt><tt> ;-- return index of closest
latitude to 13 deg<br>
</tt><tt> <font color="#3333ff"><b>lon80</b></font> =
closest_val(80,lon)</tt><tt> ;-- return index of closest
longitude to 80 deg<br>
</tt><tt><br>
</tt><tt> print("lat({13}) (closest value) = "+<font color="#ff0000"><b>lat({13})</b></font>+" Index of
closest_val: "+<font color="#3333ff">lat13</font>)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt> print("lon({80})</tt><tt><tt> (closest value)</tt> = "+<font color="#ff0000"><b>lon({80})</b></font>+" Index of
closest_val: "+<font color="#3333ff">lon80</font>)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt><br>
</tt><tt> lat_box = <font color="#009900">lat(lat13-2:lat13+2)</font></tt><tt>
;-- using indices to get the lats around lat 13 deg.<br>
</tt><tt> lon_box = <font color="#009900">lon(lon80-2:lon80+2)</font></tt><tt>
;-- using indices to get the lons around lon 80 deg.<br>
</tt><tt><br>
</tt><tt> print(""+lat_box)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt> print(""+lon_box)</tt><tt><br>
</tt><tt> print("--------------------------------------")</tt><tt><br>
</tt><tt><br>
</tt><tt> lat_box2 = lat({lat13-2:lat13+2})</tt><tt> ;-- Don't do
this: this would use the index as latitude value !!<br>
</tt><tt> lon_box2 = lon({lon80-2:lon80+2})</tt><tt> ;-- Don't do
this: this would use the index as longitude value !!</tt><tt><br>
<br>
</tt><tt> print(""+lat_box2)</tt><tt><br>
</tt><tt> print(""+lon_box2)</tt><tt><br>
</tt><tt> print("------------------")</tt><br>
<br>
It will returns, e.g<br>
<br>
<tt>(0) lat({13})</tt><tt><tt> (closest value)</tt> = <font color="#ff0000"><b>12.12418712345578</b></font> Index of
closest_val: <font color="#3333ff"><b>41</b></font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) lon({80})</tt><tt><tt> (closest value)</tt> = <font color="#ff0000"><b>80.625</b></font> Index of
closest_val: <font color="#3333ff"><b>139</b></font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) <font color="#009900">15.85470386969488</font></tt><tt><br>
</tt><tt>(1) <font color="#009900">13.98944571235667</font></tt><tt><br>
</tt><tt>(2) <font color="#009900">12.12418712345578</font></tt><tt>
; <--- closest value<br>
</tt><tt>(3) <font color="#009900">10.25892816800639</font></tt><tt><br>
</tt><tt>(4) <font color="#009900">8.393668907692385</font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) <font color="#009900">76.875</font></tt><tt><br>
</tt><tt>(1) <font color="#009900">78.75</font></tt><tt><br>
</tt><tt>(2) <font color="#009900">80.625</font></tt><tt>
; <--- closest value<br>
</tt><tt>(3) <font color="#009900">82.5</font></tt><tt><br>
</tt><tt>(4) <font color="#009900"> 84.375</font></tt><tt><br>
</tt><tt>(0) --------------------------------------</tt><tt><br>
</tt><tt>(0) 40.1029793042494</tt><tt> </tt><tt>;-- Don't do
this: this would use the index as latitude value !!<br>
</tt><tt>(1) 41.96822026907537</tt><tt><b> </b> </tt><tt>;--
Don't do this: this would use the index as latitude value !!<br>
</tt><tt>(0) 138.75</tt><tt> </tt><tt>;-- Don't do
this: this would use the index as longitude value !!<br>
</tt><tt>(1) 140.625</tt><tt> </tt><tt>;-- Don't do
this: this would use the index as longitude value !!<br>
</tt><tt>(0) ------------------</tt><br>
<br>
<br>
<br>
</div></div><div>Am 26.01.16 um 15:43 schrieb Karin
Meier-Fleischer:<br>
</div><div><div class="h5">
<blockquote type="cite">
Do you mean something like <tt>var({lat13-2:lat13+2},{lon80-2:lon80+2})</tt>
?<br>
<br>
Then the answer is no, the coordinate subscripting gets the value
of the <br>
closest grid cell and not the indices.<br>
<br>
<tt>lat({13})</tt> will use the latitude value which is the
closest to 13 degrees, e.g. 12.12418.<br>
<br>
Let us assume the following snippet of a script:<br>
<br>
<tt> <font color="#3333ff"><b>lat13</b></font> =
closest_val(13,lat)</tt><tt> ;-- return index of closest
latitude to 13 deg<br>
</tt><tt> <font color="#3333ff"><b>lon80</b></font> =
closest_val(80,lon)</tt><tt> ;-- return index of closest
longitude to 80 deg<br>
</tt><tt><br>
</tt><tt> print("lat({13}) (closest value) = "+<font color="#ff0000"><b>lat({13})</b></font>+" Index of
closest_val: "+<font color="#3333ff">lat13</font>)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt> print("lon({80})</tt><tt><tt> (closest value)</tt> = "+<font color="#ff0000"><b>lon({80})</b></font>+" Index of
closest_val: "+<font color="#3333ff">lon80</font>)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt><br>
</tt><tt> lat_box = lat(<font color="#3333ff">lat13</font>-2:<font color="#3333ff">lat13</font>+2)</tt><tt> ;-- using indices
to get the lats around lat 13 deg.<br>
</tt><tt> lon_box = lon(<font color="#3333ff">lon80</font>-2:<font color="#3333ff">lon80</font>+2)</tt><tt> ;-- using indices
to get the lons around lon 80 deg.<br>
</tt><tt><br>
</tt><tt> print(""+lat_box)</tt><tt><br>
</tt><tt> print("------------------")</tt><tt><br>
</tt><tt> print(""+lon_box)</tt><tt><br>
</tt><tt> print("--------------------------------------")</tt><tt><br>
</tt><tt><br>
</tt><tt> lat_box2 = <font color="#009900"><b>lat({lat13-2:lat13+2})</b></font></tt><tt>
;-- Don't do this: this would use the index as latitude value !!<br>
</tt><tt> lon_box2 = <font color="#009900"><b>lon({lon80-2:lon80+2})</b></font></tt><tt>
;-- Don't do this: this would use the index as longitude value
!!</tt><tt><br>
<br>
</tt><tt> print(""+lat_box2)</tt><tt><br>
</tt><tt> print(""+lon_box2)</tt><tt><br>
</tt><tt> print("------------------")</tt><br>
<br>
It will returns, e.g<br>
<br>
<tt>(0) lat({13})</tt><tt><tt> (closest value)</tt> = <font color="#ff0000"><b>12.12418712345578</b></font> Index of
closest_val: <font color="#3333ff"><b>41</b></font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) lon({80})</tt><tt><tt> (closest value)</tt> = <font color="#ff0000"><b>80.625</b></font> Index of
closest_val: <font color="#3333ff"><b>139</b></font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) <font color="#009900">15.85470386969488</font></tt><tt><br>
</tt><tt>(1) <font color="#009900">13.98944571235667</font></tt><tt><br>
</tt><tt>(2) <font color="#009900">12.12418712345578</font></tt><tt>
; <--- closest value<br>
</tt><tt>(3) <font color="#009900">10.25892816800639</font></tt><tt><br>
</tt><tt>(4) <font color="#009900">8.393668907692385</font></tt><tt><br>
</tt><tt>(0) ------------------</tt><tt><br>
</tt><tt>(0) <font color="#009900">76.875</font></tt><tt><br>
</tt><tt>(1) <font color="#009900">78.75</font></tt><tt><br>
</tt><tt>(2) <font color="#009900">80.625</font></tt><tt>
; <--- closest value<br>
</tt><tt>(3) <font color="#009900">82.5</font></tt><tt><br>
</tt><tt>(4) <font color="#009900"> 84.375</font></tt><tt><br>
</tt><tt>(0) --------------------------------------</tt><tt><br>
</tt><tt>(0) <font color="#3333ff"><b>40.1029793042494</b></font></tt><tt>
</tt><tt>;-- Don't do this: this would use the index as latitude
value !!<br>
</tt><tt>(1) <font color="#3333ff"><b>41.96822026907537</b></font></tt><tt>
</tt><tt>;-- Don't do this: this would use the index as latitude
value !!<br>
</tt><tt>(0) <font color="#3333ff"><b>138.75</b></font></tt><tt>
</tt><tt>;-- Don't do this: this would use the
index as longitude value !!<br>
</tt><tt>(1) <b><font color="#3333ff">140.625</font></b></tt><tt>
</tt><tt>;-- Don't do this: this would use the
index as longitude value !!<br>
</tt><tt>(0) ------------------</tt><br>
<br>
<br>
Hope this helps for understanding coordinate subscripting.<br>
<br>
Bye,<br>
Karin<br>
<br>
<br>
<br>
<div>Am 26.01.16 um 15:13 schrieb Guido
Cioni:<br>
</div>
<blockquote type="cite">
Shouldn’t the coordinate subscripting do the same thing?
<div>Like say <font face="Menlo">{lat13-2:lat13+2,
lon80-2:lon80+2}</font></div>
<div>
<div>
<div style="color:rgb(0,0,0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br>
Guido Cioni</div>
<div style="color:rgb(0,0,0);font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><a href="http://guidocioni.altervista.org" target="_blank"></a><a href="http://guidocioni.altervista.org" target="_blank">http://guidocioni.altervista.org</a> </div>
</div>
<br>
<div>
<blockquote type="cite">
<div>On 26 Jan 2016, at 15:04, Karin
Meier-Fleischer <<a href="mailto:meier-fleischer@dkrz.de" target="_blank">meier-fleischer@dkrz.de</a>>
wrote:</div>
<br>
<div>
<div bgcolor="#FFFFFF" text="#000000"> Hi
Krishna,<br>
<br>
you can use the function <b><tt>closest_val</tt></b>
to retrieve an index of an value.<br>
<br>
<tt> lat13 = closest_val(13,lat)</tt><tt><br>
</tt><tt> lon80 = closest_val(80,lon)</tt><br>
<br>
<tt> print("Index: "+lat13+" -
"+lat(lat13))</tt><tt><br>
</tt><tt> print("Index: "+lon80+" -
"+lon(lon80))</tt><br>
<br>
To plot 2 more grid boxes of lat/lon than you can use
e.g.<br>
<br>
<tt> plot = gsn_csm_contour_map(wks,
var(lat13-2:lat13+2,lon80-2:lon80+2),res)</tt><br>
<br>
<br>
Bye,<br>
Karin<br>
<br>
<div>Am 26.01.16 um 14:13
schrieb Krishna C:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hi <br>
<br>
<br>
</div>
<div>Let us say i need a 2 by 2 box
around 13 degree lat and 80 degree lon . How do
i know the respective indices.<br>
</div>
<div>Please correct if i am wrong. <br>
</div>
</div>
<div class="gmail_extra"><br clear="all">
<div>
<div>
<div dir="ltr">
<div style="text-align:left"><font size="2"><span style="font-family:times new roman,serif"><font size="2">R</font>egards<br>
</span></font></div>
<div style="text-align:left"><font face="verdana,sans-serif"><font size="2"><span style="font-family:times new roman,serif">-Krishna-</span></font></font><br>
</div>
</div>
</div>
</div>
<br>
<div class="gmail_quote">On Tue, Jan 26, 2016 at
5:14 PM, Guido Cioni <span dir="ltr"><<a href="mailto:guidocioni@gmail.com" target="_blank"></a><a href="mailto:guidocioni@gmail.com" target="_blank">guidocioni@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<p dir="ltr">Yes there is, but you
should have a look at the documentation on
the page ;-)<br>
The function that you need is dim_avg_n,
then you just need to restrict the latitude
and longitude with brackets {43:45}. Again,
just go on ncl documentation and you'll
definitely find a way </p>
<div class="gmail_quote">
<div>
<div>Il 26 gen 2016 11:52 AM,
"Krishna C" <<a href="mailto:chandrakrishna.90@gmail.com" target="_blank"></a><a href="mailto:chandrakrishna.90@gmail.com" target="_blank">chandrakrishna.90@gmail.com</a>>
ha scritto:<br type="attribution">
</div>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<div>
<div dir="ltr">
<div>
<div>Hi,<br>
<br>
<br>
</div>
I am trying to extract
precipitation values from WRF
output, over a small 2 by 2 lat
lon box and average it. Is there
any explicit way of doing it in
ncl<br>
<br>
</div>
<div>With warm regards<br>
<br>
</div>
<div>
<div>
<div>
<div>
<div>
<div>
<div dir="ltr">
<div style="text-align:left"><font size="2"><span style="font-family:times new roman,serif"><br>
</span></font></div>
<div style="text-align:left"><font face="verdana,sans-serif"><font size="2"><span style="font-family:times new roman,serif">-Krishna-</span></font></font><br>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
</div>
</div>
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</div></div><pre cols="72">--
Dipl. Geophys. Karin Meier-Fleischer
Visualization, NCL
Application Support
Deutsches Klimarechenzentrum GmbH (DKRZ)
Bundesstrasse 45a - D20146 Hamburg - Germany
Phone: <a href="tel:%2B49%20%280%2940%20460094%20126" value="+4940460094126" target="_blank">+49 (0)40 460094 126</a>
Fax: <a href="tel:%2B49%20%280%2940%20460094%20270" value="+4940460094270" target="_blank">+49 (0)40 460094 270</a>
E-Mail: <a href="mailto:meier-fleischer@dkrz.de" target="_blank">meier-fleischer@dkrz.de</a>
URL: <a href="http://www.dkrz.de" target="_blank">www.dkrz.de</a>
Geschäftsführer: Prof. Dr. Thomas Ludwig
Sitz der Gesellschaft: Hamburg
Amtsgericht Hamburg HRB 39784
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