| Plotting lookback time (in Gyrs) and redshift on two x axis in IDL [message #89770] |
Wed, 03 December 2014 03:47  |
johndraper1993
Messages: 3
Registered: December 2014
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Junior Member |
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Hey, I recently came across this forum which discusses the difficulties in plotting two different x axis on the same plot.
https://groups.google.com/forum/#!topic/comp.lang.idl-pvwave /_ooU4X875i0
One contributer wrote
"IDL> plot,indgen(10),YRANGE=[1,12],YTITLE='first linear
axis',YSTYLE=9,POSITION=[.1,.1,.9,.9],CHARSIZE=2
IDL>
axis,YSTYLE=1,YAXIS=1,YTICKFORMAT='conv_axis',CHARSIZE=2,YTI TLE='second
non-linear axis'
where 'conv_axis' is the name of the function which does the
conversion (e.g.):
function conv_axis,axis,index,value
return,string(FORMAT='(F0.1)',value^1.5*exp(-value^2/100))
end"
I tried to use what this user wrote in my code:
window,0
plot,res,rho*5000,/Ylog,XTITLE='Time (Gyr)',YTITLE='Log(dp/dt) (Solar Mass Mpc^-3 yr^-1)', XRange=[12,0] ;plot z against phi
axis, XAXIS=1,XTICKFORMAT=z,XTITLE='redshift'
Note: res is the time in gigayears given here:
res=9.777505969(2./3/h/sqrt(1.omega_m))*asin(sqrt((1.omega_m )/omega_m)/(1.+z)^(3./2)) ;turns z into Giga years
I was unsure what function to set equal to XTICKFORMAT, do i need to create a function to convert Gigayears into redshift?
Please say if you would like to see any more of the code, as it is quite long i left most of it out.
Thanks in advance, John
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| Re: Plotting lookback time (in Gyrs) and redshift on two x axis in IDL [message #89793 is a reply to message #89770] |
Wed, 03 December 2014 12:12  |
rryan%stsci.edu
Messages: 16
Registered: October 2014
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Junior Member |
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I don't know... But I found it to be a lot more obvious what's going on if you just do what Fanning teaches us:
http://www.idlcoyote.com/tips/another_yaxis.html
http://www.idlcoyote.com/tips/irregular_tick_spacing.html
note, for the second one, you can use the xtickv keyword and just set it equal to whatever array you want.
Russell
On Wednesday, December 3, 2014 6:47:19 AM UTC-5, johndra...@gmail.com wrote:
> Hey, I recently came across this forum which discusses the difficulties in plotting two different x axis on the same plot.
>
> https://groups.google.com/forum/#!topic/comp.lang.idl-pvwave /_ooU4X875i0
>
> One contributer wrote
>
> "IDL> plot,indgen(10),YRANGE=[1,12],YTITLE='first linear
> axis',YSTYLE=9,POSITION=[.1,.1,.9,.9],CHARSIZE=2
> IDL>
> axis,YSTYLE=1,YAXIS=1,YTICKFORMAT='conv_axis',CHARSIZE=2,YTI TLE='second
> non-linear axis'
>
> where 'conv_axis' is the name of the function which does the
> conversion (e.g.):
>
> function conv_axis,axis,index,value
> return,string(FORMAT='(F0.1)',value^1.5*exp(-value^2/100))
> end"
>
> I tried to use what this user wrote in my code:
>
> window,0
> plot,res,rho*5000,/Ylog,XTITLE='Time (Gyr)',YTITLE='Log(dp/dt) (Solar Mass Mpc^-3 yr^-1)', XRange=[12,0] ;plot z against phi
> axis, XAXIS=1,XTICKFORMAT=z,XTITLE='redshift'
>
> Note: res is the time in gigayears given here:
> res=9.777505969(2./3/h/sqrt(1.omega_m))*asin(sqrt((1.omega_m )/omega_m)/(1.+z)^(3./2)) ;turns z into Giga years
>
> I was unsure what function to set equal to XTICKFORMAT, do i need to create a function to convert Gigayears into redshift?
>
> Please say if you would like to see any more of the code, as it is quite long i left most of it out.
>
> Thanks in advance, John
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| Re: Plotting lookback time (in Gyrs) and redshift on two x axis in IDL [message #89818 is a reply to message #89795] |
Thu, 04 December 2014 12:40 |
rryan%stsci.edu
Messages: 16
Registered: October 2014
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Junior Member |
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On Wednesday, December 3, 2014 4:56:59 PM UTC-5, johndra...@gmail.com wrote> I understand that i can make one axis logarithmic in scale but i don't think this helps me as redshift isn't logarithmic with respect to lookback time (res).
>
> I have worked out what redshift is with respect to lookback time in Gyrs:
>
> z=(sqrt((1.-omega_m)/omega_m)/sin(res*3*h*sqrt((1.-omega_m)/ (2*9.777505969))))
>
> Do you know if there is there anyway i can set the top axis to have this scaling within some set of values?
>
> please say if i haven't made it clear
>
> Thanks, John
The functional form you choose is irrelevant.
(1) Pick some redshifts for which you want the lookback time.
(2) compute the lookback time. You keep giving that equation, and I think that's wrong. Where is Omega_lambda? where is time? Look at galage() in the astrolib. that is what you want.
(3) now use the z values posited above with xtickv, xtickname, and axis to put the plot where you want.
xr=[0,10]
yr=[0,1]
z=[1,2,3,4] ;redshifts to compute LB time for...
;Univ age at some redshift:
t=galage(z,1000.,h0=69.6,omega=0.286,lambda=0.714,/sil)/1.0e 9
;Univ age at today
t0=galage(0.,1000.,h0=69.6,omega=0.286,lambda=0.714,/sil)/1. 0e9
;LB time is difference...
lb=t0-t
;draw the plot
plot,[0],[0],xr=xr,xst=9,yr=yr,yst=1 ;set xst=9 to leave the top axis empty
;more plotting here
;draw the top axis
axis,xaxis=1,xr=xr,xst=1,xtickv=z,xtickname=string(lb,f='(F4 .1)'),$
xticks=n_elements(z)-1
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