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<div>Bithi</div>
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<div>You will have constant values in the SIC array anywhere that is a) land, b) perenially ice covered or c) never ice covered. Any of these conditions are physically plausible for some data points in either the Arctic or Southern Ocean, and you would get
the same warning with a regular cross-correlation using escort()</div>
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<div>In short, it's not (necessarily) a problem and is encountered in almost all gridded ocean data.</div>
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<div>Will</div>
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<span style="font-weight:bold">From: </span>Bithi De <<a href="mailto:bde@purdue.edu">bde@purdue.edu</a>><br>
<span style="font-weight:bold">Date: </span>Thursday, 17 December 2015 10:19 AM<br>
<span style="font-weight:bold">To: </span>"<a href="mailto:ncl-talk@ucar.edu">ncl-talk@ucar.edu</a>" <<a href="mailto:ncl-talk@ucar.edu">ncl-talk@ucar.edu</a>><br>
<span style="font-weight:bold">Subject: </span>[ncl-talk] How to resolve SVD warning: column contains constant<br>
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<p>Hi All,</p>
<p>I am calculating SVD between seaice concentration anomaly (documentation of the data at
<a href="http://nsidc.org/data/docs/daac/nsidc0079_bootstrap_seaice.gd.html">http://nsidc.org/data/docs/daac/nsidc0079_bootstrap_seaice.gd.html</a> ) and geopotential height anomaly from ERA-interim data, for winter(35years). I am not getting any error until
the step for calculating SVD. <br>
</p>
<p>The part of my code is as follows:</p>
<p>;***********************************************************<br>
; calculate SVD<br>
;**************************************************<br>
; Z-anomaly (timexlatxlon)<br>
</p>
<p> nxy = dimsizes(lon1)*dimsizes(latz) ;size(space)<br>
ntim = 35 ;size(time)<br>
<br>
; reorder so time varying fast <br>
; create spacextime matrix for Z_ano</p>
<p><br>
Z = z_djf(longitude|:,latitude|:,time|:)<br>
printVarSummary(Z)<br>
Z2 = onedtond(ndtooned(Z),(/nxy,ntim/)) ;convert into spacextime matrix<br>
printVarSummary(Z2)<br>
printMinMax(Z2,True)<br>
<br>
Z2!0="space"<br>
Z2!1="time"<br>
<br>
</p>
<p> <a href="mailto:Z2@_FillValue=0.0">Z2@_FillValue=0.0</a><br>
delete(Z2@_FillValue)<br>
printVarSummary(Z2)<br>
printMinMax(Z2,True)<br>
<br>
if(any(ismissing(Z2))) then<br>
print("Your data contains some missing values. Beware.")<br>
end if ; did not get any error<br>
<br>
;********* SIC anomaly *********************<br>
; create spacextime matrix for sic_ano(timex448x304) ; 448rows x304columns in 25kmx25km grid<br>
<br>
<br>
xy=448*304<br>
si = ice_djf(::-1,::-1,::-1) ;dimension reordering -->448x304xtime<br>
printVarSummary(si)</p>
<p><br>
Si2 = onedtond(ndtooned(si),(/xy,ntim/)) ;convert into (spacextime)<br>
printVarSummary(Si2)<br>
printMinMax(Si2,True)</p>
<p>Si2!0="space"<br>
Si2!1="time"<br>
<br>
<a href="mailto:Si2@_FillValue=0.0">Si2@_FillValue=0.0</a><br>
delete(Si2@_FillValue)<br>
printVarSummary(Si2)<br>
printMinMax(Si2,True)<br>
<br>
if(any(ismissing(Si2))) then<br>
print("Your data contains some missing values. Beware.")<br>
end if ; did not get any error<br>
<br>
<br>
; check if some columns has constant value<br>
p2d=Si2(time|:,space|:)<br>
printVarSummary(p2d)<br>
<br>
p2d_dims = dimsizes(p2d) ; I assume this is time x p1d<br>
<br>
ntim = p2d_dims(0)<br>
np1d = p2d_dims(1)<br>
<br>
;do i=0,np1d-1<br>
;pmin = min(p2d(:,i))<br>
; pmax = max(p2d(:,i))<br>
;if(pmin.eq.pmax) then<br>
; print("p2d contains all constant values at np1d = " + i)<br>
;end if<br>
;end do <br>
exit<br>
<br>
; delete([/Z,Zano,SIC,si/])<br>
<br>
;***************************************************<br>
;spatial plot of 1st mode of left and right singular vector<br>
;************************************************************* <br>
<br>
nsvd = nxy<br>
svLeft = new((/nsvd,nxy/),float) ; pre-allocate space<br>
svRight = new((/nsvd,xy/),float) <br>
<br>
pc = svdcov_sv(Z2,Si2,nsvd,svLeft,svRight)<br>
<br>
printVarSummary(pc) </p>
<p> end<br>
</p>
<p>;; giving warning ==> all Y values in columns are missing or constant</p>
<h1>*********</h1>
<p>I checked for Si2 following the <a id="LPlnk886053" href="http://www.ncl.ucar.edu/Support/talk_archives/2011/2803.html">
http://www.ncl.ucar.edu/Support/talk_archives/2011/2803.html</a> and it is shows it has constant value.
<br>
</p>
<p>Could you suggest how I can solve it?</p>
<p><br>
</p>
<p>Thanks in advance!</p>
<p>Bithi De</p>
<p>Purdue University<br>
</p>
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<p></p>
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