baseOlig.error.step1 {LPE} | R Documentation |
Genes are placed in bins/quantiles according to their average expression intensity. The function baseOlig.error calculates a pooled variance of M for genes within these bins/quantiles of A for the replicates of the experimental condition contained in y. Here the assumption is that variance of the genes in each interval is similar.
baseOlig.error.step1(y, stats=median, q=0.01, df=10)
y |
y is a preprocessed matrix or data frame of expression intensities in which columns are expression intensities for a particular experimental condition and rows are genes. |
stats |
It determines whether mean or median is to be used for the replicates |
q |
q is the quantile width; q=0.01 corresponds to 100 quantiles i.e. percentiles. Bins/quantiles have equal number of genes and are split according to the average intensity A. |
df |
df stands for degrees of freedom. It is used in smooth.spline function to interpolate the variances of all genes. Default value is 10. |
Returns object of class baseOlig, comprising a data frame with 2 columns: A and var M. The A column contains the median values of each gene and the M columns contains the corresponding variance. Number of rows of the data-frame is same as that of the number of genes.
Nitin Jainnitin.jain@pfizer.com
J.K. Lee and M.O.Connell(2003). An S-Plus library for the analysis of differential expression. In The Analysis of Gene Expression Data: Methods and Software. Edited by G. Parmigiani, ES Garrett, RA Irizarry ad SL Zegar. Springer, NewYork.
Jain et. al. (2003) Local pooled error test for identifying differentially expressed genes with a small number of replicated microarrays, Bioinformatics, 1945-1951.
Jain et. al. (2005) Rank-invariant resampling based estimation of false discovery rate for analysis of small sample microarray data, BMC Bioinformatics, Vol 6, 187.
# Loading the library and the data library(LPE) data(Ley) dim(Ley) # Gives 12488 by 7 Ley[1:3,] # Returns # ID c1 c2 c3 t1 t2 t3 # 1 AFFX-MurIL2_at 4.06 3.82 4.28 11.47 11.54 11.34 # 2 AFFX-MurIL10_at 4.56 2.79 4.83 4.25 3.72 2.94 # 3 AFFX-MurIL4_at 5.14 4.10 4.59 4.67 4.71 4.67 Ley[1:1000,2:7] <- preprocess(Ley[1:1000,2:7],data.type="MAS5") # Finding the baseline distribution of subset of the data # condition one (3 replicates) var.1 <- baseOlig.error.step1(Ley[1:1000,2:4], q=0.01) dim(var.1) # Returns a matrix of 1000 by 2 (A,M) format