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astro (version 1.2)

schechter.fit: Fit to the Schechter Function

Description

This function calculates a Schechter function fit to a set of input data.

Usage

schechter.fit(data, vmax = NA, knee, slope, norm, knee.alt = NA, slope.alt = NA, norm.alt = NA, kneelo = -Inf, slopelo = -Inf, normlo = 0, kneehi = Inf, slopehi = Inf, normhi = Inf, fixk1 = FALSE, fixs1 = FALSE, fixn1 = FALSE, fixk2 = FALSE, fixs2 = FALSE, fixn2 = FALSE, range = range(data), lim1 = NA, lim2 = NA, numlim = 1, method = "nlminb", volume = max(vmax), bw = 0.1, mag = FALSE, log = FALSE, null = 1E-9, error = "jack", subvol = 10, sampnum = subvol, msun = solar("r"))

Arguments

data
input data vector
vmax
vector of maximum comoving volumes within which object could lie
knee
the knees(s) of the Schechter function (L_star/M_star)
slope
the slope(s) of the Schechter function (alpha)
norm
the normalisation(s) of the Schechter function (phi_star)
knee.alt
alternative knees(s) of the Schechter function (L_star/M_star)
slope.alt
alternative slope(s) of the Schechter function (alpha)
norm.alt
alternative normalisation(s) of the Schechter function (phi_star)
kneelo
a lower bound on the knee parameter
slopelo
a lower bound on the slope parameter
normlo
a lower bound on the norm parameter
kneehi
an upper bound on the knee parameter
slopehi
an upper bound on the slope parameter
normhi
an upper bound on the norm parameter
fixk1
fix the first knee?
fixs1
fix the first slope?
fixn1
fix the first normalisation?
fixk2
fix the second knee?
fixs2
fix the second slope?
fixn2
fix the second normalisation?
range
data range of interest
lim1
lower data limit for fitting
lim2
upper data limit for fitting
numlim
lower number (per bin) limit for fitting
method
choice of 'nlminb' (recommended) or one of 'optim's minimisation methods (e.g., 'Nelder-Mead')
volume
total volume across which the data has been collected (default 1 if vmax = NA)
bw
bin width sizes
mag
are the input data magnitudes?
log
are the input data logged?
null
value of null
error
parameter error estimation method [jack/boot]
subvol
number of sub-volumes to split the input data into
sampnum
number of samplings to be made for bootstrapping method
msun
absolute magnitude of the sun (to be used in calculation of the luminosity density should mag=TRUE)

Value

binmid
bin midpoints
num
number per bin
den
density per bin
err
error per bin
errlo
lower error limit
errhi
upper error limit
par
best fit parameters
parlo
lower error estimates on recovered fit parameters
parhi
upper error estimates on recovered fit parameters
j
luminosity density
jlo
lower luminosity density limit
jhi
upper luminosity density limit
chi2
chi2 value
dof
number of degrees of freedom
rchi2
reduced chi2
pval
probability of observing chi2 value by chance [significant: pval < 0.05]
denlim
lower density limit used
hessian
optim hessian output

References

Blanton M. R., Lupton R. H., Schlegel D. J., Strauss M. A., Brinkmann J., Fukugita M., Loveday J., 2005, ApJ, 631, 208

Driver S. P., Popescu C. C., Tuffs R. J., Graham A. W., Liske J., Baldry I., 2008, ApJ, 678, L101

Baldry I. K. Driver S. P., Loveday J., et al., 2012, MNRAS, 421, 621

See Also

The astronomy package: astro.