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--- archive:bioinformatic_tools:velvet [2010/04/14 09:19]
galt
+++ archive:bioinformatic_tools:velvet [2015/07/28 06:27] (current)
ceisenhart ↷ Page moved from bioinformatic_tools:velvet to archive:bioinformatic_tools:velvet
@@ Line 14: / Line 14: @@
 On wikipedia: [[wp>Velvet_(software)|Velvet]].
+[[http://www.ebi.ac.uk/training/ftp/PhDtheses/Daniel_Zerbino.pdf|Daniel Zerbino's PhD Thesis on Velvet]]
 Velvet has support for COLORSPACE, possibly the only de-novo short-read DBG assembler that does at this time.
+The colorspace version of velvet (_de) expects all data to be double-encoded. Mixed-space not directly supported.
 Velvet has support for long-read data.
-=== Installing ===
+Velvet will accept sequence data from fastq input files, but does not use the quality information.
-  ssh campusrocks.cse.ucsc.edu
+==== Color-Space ====
-  cd /campusdata/BME235/programs
-  wget http://www.ebi.ac.uk/~zerbino/velvet/velvet_0.7.62.tgz
-  tar xfz velvet_0.7.62.tgz
-  mv velvet_0.7.62 velvet
-  mv velvet_0.7.62.tgz velvet/
-  cd velvet
-  make
-  make color
-  # color versions work with solid, have _de extension
-  # install to bin dir
-  cp velveth velvetg velveth_de velvetg_de /campusdata/BME235/bin/
+=== DE double-encoded ===
-De-novo Tools for velvet from ABI for Solid.
-http://solidsoftwaretools.com/gf/project/denovo/
-=== Color-Space ===
-== DE double-encoded ==
 This is done by the pre-processor.
 The primer base from the colorspace read is
@@ Line 53: / Line 38: @@
 and then re-encoded as if bases in base-space.
-== colorspace programs ==
+=== colorspace programs ===
 denovo_preprocessor
@@ Line 71: / Line 56: @@
 to base-space while reducing read errors in colorspace as much as possible.
-=== Examples ===
+[[http://solidsoftwaretools.com/gf/project/denovo/|De-novo Tools for velvet from ABI for Solid]]
+==== Running ====
+Strategy:
+  - Find the right value for k.  For short reads remember to keep k small for good kmer coverage.
+  - Find the right values for exp_cov and cov-cutoff. This is very important.
+    * velvet-estimate-exp_cov.pl out/stats.txt makes a useful graph.
+  - If you only have long reads, use them also as your short reads.
+For 454 long reads, this was our best result:
+  velveth out 31 -short 454/?.TCA.454Reads.fna -long 454/?.TCA.454Reads.fna
+  velvetg out -exp_cov 60 -cov_cutoff 13
+  Final graph has 1755 nodes and n50 of 41723, max 142286, total 2468925, using 778257/782604 reads
+==== Failures ====
+=== VelvetOptimiser ===
+The contributed (velvet/contrib/) utility VelvetOptimiser is intended to help find
+the critical parameters k, exp_cov, and cov_cutoff.  However although it found k,
+it got stuck on a local maximum on coverage and failed to produce anything useful.
+=== pseudoFlow ===
+Wondering if homopolymer errors in 454 data could cause trouble for the DBG,
+I made a utility called pseudoFlow.c that takes all homopolymers longer than
+and shortens them to 6.  We know that in the range 1 to 6, 454 is accurate.
+In any case, the pseudoFlow version of the data did not perform better,
+in fact it was a little worse.
+==== Installing ====
+  ssh campusrocks.cse.ucsc.edu
+  cd /campusdata/BME235/programs
+  wget http://www.ebi.ac.uk/~zerbino/velvet/velvet_0.7.62.tgz
+  tar xfz velvet_0.7.62.tgz
+  mv velvet_0.7.62 velvet
+  mv velvet_0.7.62.tgz velvet/
+  cd velvet
+  make
+  make color
+  # color versions work with solid, have _de extension
+  # install to bin dir
+  cp velveth velvetg velveth_de velvetg_de /campusdata/BME235/bin/
+==== Examples ====
 [[http://kevin-gattaca.blogspot.com/2009/12/de-novo-assembly-with-abi-solid-reads.html|example of using velvet with solid]]

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