linear interpolation functions in grads-2.0.a5.oga.5

[James T. Potemra]

I'm running grads-2.0.a5.oga.5 on a 64-bit linux machine and want to do
a linear
fit to a time-series.  There appears to be a UDF called "linreg" that is
included
in Mike Fiorino's UDF library, but the man page at
http://opengrads.org/doc/udxt/libmf/
does not list this function.

Conversely, there is a man page for "tregr2" at
http://opengrads.org/doc/udxt/libbjt/
as part of Ben-Jei Tsuang's UDF library, but that does not appear in the
UDC list
(see list below).

I would like to plot a linear fit through a time-series of a particular
variable.  It looks
like either of these would do this, but in my case the independent
variable is time, and
I'm not sure if I need to somehow define that in the Y = m * X + b
syntax for either
tregr2 or linreg.

I'd appreciate any suggestions.  Thanks,

Jim

------------------------------------------------------------------------------------------------------

ga-> q udf

   User
  Defined
  FUNCTION          Short Description                Function at Library
 ---------- -----------------------------------  --------------------------
 lt         Less than operator                   f_bjt@^libbjt.gex
 jd         Julian day                           f_bjt@^libbjt.gex
 cosz       Cosine solar zenith angle            f_bjt@^libbjt.gex
 dayratio   Daylight ratio                       f_bjt@^libbjt.gex
 if         Conditional function                 f_bjt@^libbjt.gex
 maxv       Maximum value                        f_bjt@^libbjt.gex
 minv       Minimum value                        f_bjt@^libbjt.gex
 which      Label gridpoints                     f_bjt@^libbjt.gex
 ftest      F-test                               f_bjt@^libbjt.gex
 ttest      T-test                               f_bjt@^libbjt.gex
 tfit       Point  linear regression             f_bjt@^libbjt.gex
 fit        Global linear regression             f_bjt@^libbjt.gex
 tcorr2     Time correlation                     f_bjt@^libbjt.gex
 tregr2     Point linear regression              f_bjt@^libbjt.gex
 tmave2     Time averaging w/masking             f_bjt@^libbjt.gex
 madvu      Calculates -d(u*EXPR)/dx             f_bjt@^libbjt.gex
 madvv      Calculates -d(V*EXPR)/dy             f_bjt@^libbjt.gex
 madvw      Calculates -d(W*EXPR)/dp             f_bjt@^libbjt.gex
 muadv      Zonal advection                      f_bjt@^libbjt.gex
 mvadv      Meridional advection                 f_bjt@^libbjt.gex
 mwadv      Vertical advection                   f_bjt@^libbjt.gex
 satvap     Saturated vapor pressure             f_bjt@^libbjt.gex
 dew        Dew point temperature                f_bjt@^libbjt.gex
 lw         Thermal infrared fluxes              f_bjt@^libbjt.gex
 lw2        Thermal infrared fluxes v2           f_bjt@^libbjt.gex
 pinterp    Pressure interpolation               f_bjt@^libbjt.gex
 zinterp    Height interpolation                 f_bjt@^libbjt.gex
 line       Draws a line                         f_bjt@^libbjt.gex
 vint2      Mass-weighted vertical integral      f_bjt@^libbjt.gex
 fish       Poisson solver                       f_fish@^fish.gex
 fish_psi   Compute streamfunction               f_psichi@^fish.gex
 fish_chi   Compute velocity potential           f_psichi@^fish.gex
 fish_vor   Compute vorticity                    f_psichi@^fish.gex
 fish_div   Compute divergence                   f_psichi@^fish.gex
 dewpt      Dew-point temperature                f_gsudf@^gsudf.gex
 ept        Equivalent potential temperature     f_gsudf@^gsudf.gex
 epi        Potential Instability                f_gsudf@^gsudf.gex
 plcl       Pressure at LCL                      f_gsudf@^gsudf.gex
 shear      Wind Shear                           f_gsudf@^gsudf.gex
 srh1km     Storm-relative Helicity 0-1km'       f_gsudf@^gsudf.gex
 srh3km     Storm-relative Helicity 0-3km'       f_gsudf@^gsudf.gex
 tlcl       Temperature at LCL                   f_gsudf@^gsudf.gex
 tsindex    Chance of T-storm Initiation         f_gsudf@^gsudf.gex
 ttindex    Total Totals Index                   f_gsudf@^gsudf.gex
 wchill     Wind Chill Index (New)               f_gsudf@^gsudf.gex
 hello      Hello, World! sample function        f_hello@^libhello.gex
 ipc_save   Save expression to stream            f_Save@^libipc.gex
 ipc_load   Load variable from file              f_Load@^libipc.gex
 smth2d     Shuman smoother/de-smoother          f_smth2d@^libmf.gex
 uv2trw     Find radial/tangential velocity      f_uv2trw@^libmf.gex
 re2        General interpolator (regrid2)       f_re2@^libmf.gex
 esmrf      Saturation vapor pressure (old MRF)  f_esmrf@^libmf.gex
 linreg     Linear regression: mx + b            f_linreg@^libmf.gex
 re         General interpolator                 ffre@^re.gex
 re_        General interpolator (verbose)       ffre_dbg@^re.gex
 regrid2    regrid2-like wrapper for re()        f_gsudf@^gsudf.gex
 reimg      Interpolation for Image Generation'  f_gsudf@^gsudf.gex
 sh_filt    Spherical harmonic filter            f_shfilt@^shfilt.gex
 sh_power   Spherical harmonic spectra           f_shpowr@^shfilt.gex
 ---------- -----------------------------------  --------------------------