# [ncl-talk] Frequency to days conversion and draw a vertical line in the plot

Nanda Kishore Reddy nandu.eng at gmail.com
Mon Mar 14 01:30:44 MDT 2016

```Thanks Dennis. I have got the plot what exactly I need.

With Kind Regards
Nanda Kishore reddy. B
Senior Research Fellow
Ocean Observation Systems
NIOT

On Sat, Mar 12, 2016 at 1:42 AM, Dennis Shea <shea at ucar.edu> wrote:

> See Example 5 at:
>     http://www.ncl.ucar.edu/Applications/spec.shtml
>
> Good Luck
>
> On Thu, Mar 10, 2016 at 5:32 AM, Nanda Kishore Reddy <nandu.eng at gmail.com>
> wrote:
>
>> Hi ncl-users,
>>
>>                 I am very new to the NCL software and I would like to do
>> spectrum analysis with confidence levels. I have tried with the existing
>> code and plotted, but, I just need some help like how to plot x-axis in the
>> form of *Days *(i.e. 1/frequency) instead of the *frequency (days/cycle)
>> *otherwise top axis should be in Days and bottom axis should be in
>> frequency (if it is possible).
>>                 I have, just need one more help like how to draw a
>> vertical line in the plot (x=0.05,y=1000) from the below attached figure.
>>
>>
>>
>> begin
>>
>> d   = 0        ; detrending opt: 0=>remove mean 1=>remove mean + detrend
>> sm  = 0        ; smooth: should be at least 3 and odd
>> pct = 0.1      ; percent taper: (0.0 <= pct <= 1.0) 0.10 common.
>>
>> ;************************************************
>> ; calculate spectrum
>> ;************************************************
>> sdof = specx_anal(buoy(:,0),d,sm,pct)
>> ;print (sdof)
>> ;exit
>> ;************************************************
>> ; calculate confidence interval [here 5 and 95%]
>> ; return 4 curves to be plotted
>> ;************************************************
>> splt = specx_ci (sdof, 0.05, 0.99)
>>
>> ;************************************************
>> ; plotting
>> ;************************************************
>> wks  = gsn_open_wks("x11","spec")              ; Opens a ps file
>>
>> r = True                                                         ; plot
>> mods desired
>> r at tiMainString = "AD08 wind speed"           ; title
>> r at tiXAxisString = "Frequency (cycles/Days)"    ; xaxis
>> r at tiYAxisString = "Variance"                     ; yaxis
>> r at trYLog              = True                          ; log scaling
>> ;r at trXMinF = 0
>> ;r at trXMaxF = 0.2
>> ;r at trYMinF             = 1                            ; manually set
>> lower limit
>> ;r at trYMaxF             = 1000.0                  ;   "          upper
>> r at gsnFrame            = False                    ; do not advance frame
>> r at xyLineThicknesses   = (/2.,1.,1.,1./)
>> r at xyDashPatterns      = (/0,0,1,1/)
>> r at xyLineColors        = (/"foreground","green","blue","red"/)
>> plot  = gsn_csm_xy(wks,sdof at frq, splt,r)
>> lnid =
>>
>> xf   = (/0.40, 0.40+sdof at bw/)                ; Create band width line
>> ys   = 0.60*max(sdof at spcx)                   ; 75% up Y axis
>> yv   = (/ys,ys/)
>> rpl  = True                                                ; resources
>> for polyline
>> rpl at gsLineThicknessF  = 2                    ; Define line thickness
>> ;gsn_polyline(wks,plot,xf,yv,rpl)             ; Draw BandWidth
>>
>> txres= True                                                ; label BW line
>> txres at txFontHeightF = 0.015                  ; font height
>> txres at txJust        = "CenterLeft"               ; Set lable location
>> ;gsn_text(wks,plot,"BW",0.41+sdof at bw,ys,txres)    ; Label
>> frame (wks)
>> end
>>
>>
>>
>>
>> With Kind Regards
>> Nanda Kishore reddy. B
>> Senior Research Fellow
>> Ocean Observation Systems
>> NIOT, INDIA
>>
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>
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