Description Usage Arguments Details Value Author(s) References Examples
A function for identifying differentially expressed proteins between two sample groups using spectral counts from LC-MS/MS Experiments
1 2 | SASPECT(peptideData, pep.set, pep.pro.name, run.group.info,
permu.iter=50, filter.run=2, filter.score=0.95)
|
peptideData |
a list of two components: |
pep.set |
a character vector of length p. The ith element is the peptide ID corresponding to the ith row
of |
pep.pro.name |
a character matrix with 2 columns. The first column gives the protein IDs, and the second column gives the names of the peptides matching to the proteins in the first column. |
run.group.info |
a data frame with two columns. The first column ( |
permu.iter |
an integer. It is the number of permutation iterations for estimating FDR. The default value is 50. |
filter.run |
an integer. It is the filter criteria for removing peptides observed in too few samples. The default value is 2. |
filter.score |
a scale. PeptideConfidence scores above this value are counted in the filtering process. The default value is 0.95 |
This function implements the SASPECT-hybrid method (Wang et. al. 2008, in preparation), which is a modified version
of the original SASPECT mothod proposed in Whiteaker et. al. 2007. The Score1
column in the returned matrix gives
test statistics using the original SASPECT method.
SASPECT generates a data frame with 7 columns:
Protein |
Protein groups' ID. |
ProteinsInGroup |
Names of proteins in each protein group (separated by |
Score1 |
test score based on Appear-Absent (AA) measurements. A positive value suggests the abundence level in the second group is higher than the first group. A negative value suggests the opposite. |
Score2 |
test score based on non zero total Spectral count (SpecC) measurements. A positive value suggests the abundence level in the second group is higher than the first group. A negative value suggests the opposite. |
Score |
final SASPECT score (sum square of Score1 and Score2). |
Qvalue |
FDR resulted from permutation test based on |
PeptideNumber |
number of peptides observed for each protein(protein group). |
Wang, P. and Liu, Y.
Whiteaker, J. R., Zhang, H., Zhao, L., Wang, P., Kelly-Spratt, K. S., Ivey, R. G., Piening, B. D., Feng, L., Kasarda, E., Gurley, K. E., Eng, J. K., Chodosh, L. A., Kemp, C. J., McIntosh, M. W., Paulovich, A. G (2007) Integrated Pipeline for Mass Spectrometry-Based Discovery and Confirmation of Biomarkers Demonstrated in a Mouse Model of Breast Cancer. J. Proteome Res., 6(10); 3962-3975.
Wang, P., Liu, Y., McIntosh, M. W., Paulovich, A. G (2008) Significant analysis for comparative proteomics studies using label free LC-MS/MS experiments (in preparation).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | library(SASPECT)
data(mouseTissue)
SASPECT.result<-SASPECT(peptideData=mouseTissue$peptideData,
pep.set=mouseTissue$pep.set,
pep.pro.name=mouseTissue$pep.pro.name,
run.group.info=mouseTissue$run.group.info,
permu.iter=50,
filter.run=2,
filter.score=0.95)
### it takes about 1 minute to run this example.
### check the qvalue distribution
qvalue=as.numeric(SASPECT.result[,"Qvalue"])
plot(sort(qvalue))
### output the result into a table file
write.table(SASPECT.result, file="SASPECT.result.txt", row.names=FALSE, sep="\t")
|
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