cuffdiff output

[dnusol]

Hi, while running cuffdiff on two samples (so no replicates) I get the following message

> Processing Locus Chr1:258631-267891 [ ] 0%Error: sqrt(det(cov)) == 0, 0.000000 after rounding.
> Processing Locus Chr3:2891085-2893741 [*********** ] 45%Error: sqrt(det(cov)) == 0, 0.000000 after rounding.
> Processing Locus Chr4:16101600-16102156 [****************** ] 74%Error: sqrt(det(cov)) == 0, 0.000000 after rounding.
> Processing Locus Chr5:357740-358798 [******************* ] 77%Error: sqrt(det(cov)) == 0, 0.000000 after rounding.
Error: sqrt(det(cov)) == 0, 0.000000 after rounding.

What does it mean? is it something I should worry about?

Thanks

Dave

[pasta]

sqrt() = calculate square root
cov() = calculate covariance
det() = ?

Basically the software cannot calculate the square root of covariance which COULD BE normal since you do not use replicates. Maybe is it doing some least square calculation. I dont think I would mind If I were you

[dnusol]

Hi Pasta,

thanks for your answer. I will make some fake replicates in order to check that this issue is related to the lack of replicates.

Meanwhile I run cufflinks and cuffcompare using a downloaded GTF file as reference file but the cuffdiff output does not come out with information the gene name or locus column, so I just get the random identifier generated by cufflinks. Do you know how I can include this information?? See the following example

$ head genes.fpkm_tracking
tracking_id class_code nearest_ref_id gene_short_name tss_id locus s5_FPKM s5_conf_lo s5_conf_hi s1_FPKM s1_conf_lo s1_conf_hi
XLOC_000001 - - - TSS1,TSS2 Chr1:3617-5903 5.34002 1.73637 8.94367 82.2908 64.1985 100.383
XLOC_000002 - - - ,TSS3 Chr1:6516-8763 1.09354 0.478872 1.70821 3.2086 2.41061 4.00659
XLOC_000003 - - - ,TSS4,TSS5 Chr1:23094-33226 32.8189 32.8189 32.8189 78.4804 78.4804 78.4804
XLOC_000004 - - - ,TSS6,TSS7 Chr1:50024-51202 170.472 149.429 191.516 251.281 223.25 279.312
XLOC_000005 - - - TSS8,TSS9 Chr1:52035-54631 5.50825 0.724292 10.2922 4.23105 0.110532 8.35157
XLOC_000006 - - - TSS10 Chr1:72335-74721 24.9435 18.1258 31.7612 17.9945 10.545 25.444
XLOC_000007 - - - - Chr1:82841-85073 0 0 0 5.19902 3.8691 6.52894
XLOC_000008 - - - TSS11,TSS12 Chr1:91391-95665 9.64846 3.4351 15.8618 7.29045 1.88894 12.692
XLOC_000009 - - - TSS13,TSS14,TSS15 Chr1:95851-99241 54.1341 39.4121 68.8561 57.8228 42.5951 73.0504


Best,

Dave