Converting quanteda dfmSparse matrix->data.frame->h2o adds unwanted initial row of NaNs
<p>I have a 10025x1417 TFIDF dfm matrix created with <a href="https://cran.r-project.org/web/packages/quanteda/" rel="nofollow">quanteda</a>. (The actual class is dfmSparse which is a subclass of <a href="http://rpackages.ianhowson.com/cran/quanteda/man/dfm-class.html" rel="nofollow">dfm-matrix</a>).
When I convert to h2o with as.data.frame and then as.h2o, I incorrectly get 1002<strong>6</strong>x1417, with an unwanted extra first row of NaNs.
For performance reasons I don't want to create a temporary df with the full dense matrix.</p>

<p>The code is as follows (I was unable to reproduce on small toy data):</p>

<pre><code>library(quanteda)
mat &lt;- quanteda::weight(theDfm, type="tfidf")

# Convert to df then h2o, correctly gives 10025x1417 matrix
mat_df  &lt;- as.data.frame(mat) # this will dispatch quanteda::as.data.frame for dfmSparse
mat_h2o &lt;- as.h2o(mat_df)

# Convert in one go, get 10026x1417, get unwanted extra first row of NaNs
bad_h2o &lt;- as.h2o(as.data.frame(mat))
dim(bad_h2o )
[1] 10026  1417

# Which as.data.frame method this uses
&gt; showMethods(quanteda::as.data.frame)
Function: as.data.frame (package base)
x="ANY"
x="dfm"
x="dfmSparse"
    (inherited from: x="dfm")
x="matrix"
    (inherited from: x="ANY")

#########################################
# Ken Benoit requested sessionInfo()

R version 3.2.3 (2015-12-10)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows &gt;= 8 x64 (build 9200)

locale:
[1] LC_COLLATE=English_United States.1252  LC_CTYPE=English_United States.1252    LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                           LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] h2o_3.8.3.3         statmod_1.4.22      quanteda_0.9.8      RevoUtilsMath_3.2.3

loaded via a namespace (and not attached):
 [1] Rcpp_0.12.2      lattice_0.20-33  SnowballC_0.5.1  bitops_1.0-6     chron_2.3-47     grid_3.2.3       R6_2.1.1        
 [8] jsonlite_0.9.19  magrittr_1.5     httr_1.0.0       stringi_1.0-1    data.table_1.9.6 ca_0.58          Matrix_1.2-3    
[15] tools_3.2.3      stringr_1.0.0    RCurl_1.95-4.7   parallel_3.2.3 
</code></pre>