| Version: | 1.1-8 | 
| Title: | Computes Local False Discovery Rates | 
| Maintainer: | Balasubramanian Narasimhan <naras@stat.Stanford.EDU> | 
| License: | GPL-2 | 
| Imports: | stats, splines, graphics | 
| Description: | Computation of local false discovery rates. | 
| NeedsCompilation: | no | 
| Packaged: | 2015-07-14 19:43:25 UTC; naras | 
| Author: | Bradley Efron [aut], Brit Turnbull [aut], Balasubramanian Narasimhan [aut, cre], Korbinian Strimmer [ctb] | 
| Repository: | CRAN | 
| Date/Publication: | 2015-07-15 01:48:23 | 
HIV data set
Description
The data comprises 7680 z-values, each relating to a
two-sample t-test. The test compares gene expression values for
4 HIV patients with values for 4 normal subjects; the t-score
T[i] for gene i has been transformed to a normal scale,
z[i] = qnorm(pt(T[i], df=6)), so that the
z[i]'s theoretically would have a
standard N(0,1) distribution under the null hypothesis. The
original experiment is described in van't Wout et. al. (2003).
Usage
data(hivdata)Format
A vector containing 7680 z-values
References
van't Wout, et. al., Cellular gene expression upon human immuno-deficiency virus type 1 infection of CD4+-T-Cell lines, Journal ofVirology 77, 1392-1402.
Simulated data set for locfdr
Description
A simulated dataset that involves 2000 "genes", each of
which has yielded a test statistic "zex", with
zex[i] ~ N(mu[i],1) (independently for i=1,2,...2000.)
The data comprises 2000 \mu_i values and 2000
z-values.
Usage
data(lfdrsim)Format
A matrix of 2000 rows and 2 columns containing mu and the
z-score values (zex)
Local False Discovery Rate Calculation
Description
Compute local false discovery rates, following the definitions and description in references listed below.
Usage
locfdr(zz, bre = 120, df = 7, pct = 0, pct0 = 1/4, nulltype = 1, type =
0, plot = 1, mult, mlests, main = " ", sw = 0)
Arguments
| zz | A vector of summary statistics, one for each case under
simultaneous consideration.  The
calculations  assume a large number of cases, say
 | 
| bre | Number of breaks in the discretization of the  | 
| df | Degrees of freedom for fitting the estimated
density  | 
| pct | Excluded tail proportions of  | 
| pct0 | Proportion of the  | 
| nulltype | Type of null hypothesis assumed in estimating  | 
| type | Type of fitting used for  | 
| plot | Plots desired.  0 gives no plots. 1 gives single
plot showing the histogram of  | 
| mult | Optional scalar multiple (or vector of multiples) of the sample size for calculation of the corresponding hypothetical Efdr value(s). | 
| mlests | Optional vector of initial values for (delta0, sigma0) in the maximum likelihood iteration. | 
| main | Main heading for the histogram plot when  | 
| sw | Determines the type of output desired. 2 gives a list consisting of the last 5 values listed under Value below. 3 gives the square matrix of dimension bre-1 representing the influence function of log(fdr). Any other value of sw returns a list consisting of the first 5 (6 if mult is supplied) values listed below. | 
Details
See the locfdr vignette for details and tips.
Value
| fdr | the estimated local false discovery rate for each case, using the selected type and nulltype. | 
| fp0 | the estimated parameters delta (mean of f0), sigma (standard deviation of f0), and p0, along with their standard errors. | 
| Efdr | the expected false discovery rate for the non-null cases,
a measure of the experiment's power as described in Section 3
of the second reference.  Overall Efdr and right and left values are
given, both for the specified nulltype and for nulltype 0.  If
 | 
| cdf1 | a 99x2 matrix giving the estimated cdf of fdr under the non-null distribution f1. Large values of the cdf for small fdr values indicate good power; see Section 3 of the second reference. Set plot to 3 or 4 to see the cdf1 plot. | 
| mat | A matrix of estimates of  | 
| z.2 | the interval along the zz-axis outside of which $fdr(z)<0.2$, the locations of the yellow triangles in the histogram plot. If no elements of zz on the left or right satisfy the criterion, the corresponding element of z.2 is NA. | 
| call | the function call. | 
| mult | If the argument mult was supplied, vector of the ratios of hypothetical Efdr for the supplied multiples of the sample size to Efdr for the actual sample size. | 
| pds | The estimates of p0, delta, and sigma. | 
| x | The bin midpoints. | 
| f | The values of  | 
| pds. | The derivative of the estimates of p0, delta, and sigma with respect to the bin counts. | 
| stdev | The delta-method estimates of the standard deviations of the p0, delta, and sigma estimates. | 
Author(s)
Bradley Efron, Brit B. Turnbull, and Balasubramanian Narasimhan
References
Efron, B. (2004) "Large-scale simultaneous hypothesis testing: the choice of a null hypothesis", Jour Amer Stat Assoc, 99, pp. 96–104
Efron, B. (2006) "Size, Power, and False Discovery Rates"
Efron, B. (2007) "Correlation and Large-Scale Simultaneous Significance Testing", Jour Amer Stat Assoc, 102, pp. 93–103
http://statweb.stanford.edu/~ckirby/brad/papers/
Examples
## HIV data example
data(hivdata)
w <- locfdr(hivdata)