<div dir="ltr"><div class="markdown-here-wrapper" style><p style="margin:1.2em 0px!important">Oh nice catch! It’s not in the latest version on CRAN, but if you install the development version from github (<code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">devtools::install_github("kaneplusplus/bigmemory")</code>) you will be able to create a big matrix with a type float. You will just need to explicitly tell R to store the data as a float, i.e. <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">as.big.matrix(x, type="float")</code>. Be warned though, your print code will probably segfault when you create the arma::Mat and try to print the matrix.</p>
<div title="MDH:T2ggaW50ZXJlc3RpbmcuIEl0J3Mgbm90IGluIHRoZSBsYXRlc3QgdmVyc2lvbiBvbiBDUkFOLCBi
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IG1hdHJpeC4=" style="height:0;width:0;max-height:0;max-width:0;overflow:hidden;font-size:0em;padding:0;margin:0"></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On 2 June 2015 at 14:30, Yue Li <span dir="ltr"><<a href="mailto:gorillayue@gmail.com" target="_blank">gorillayue@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">I see. Thanks for the explanation Scott. Wish the bigmatrix will get native float type. I found a related post here: <a href="https://github.com/kaneplusplus/bigmemory/issues/4" target="_blank">https://github.com/kaneplusplus/bigmemory/issues/4</a><span class="HOEnZb"><font color="#888888"><div><br></div></font></span><div><span class="HOEnZb"><font color="#888888">Yue</font></span><div><div class="h5"><br><div><br></div><div><br><div><blockquote type="cite"><div>On Jun 2, 2015, at 12:27 AM, Scott Ritchie <<a href="mailto:sritchie73@gmail.com" target="_blank">sritchie73@gmail.com</a>> wrote:</div><br><div><div dir="ltr"><div><p style="margin:1.2em 0px!important">Hi Yue,</p><p style="margin:1.2em 0px!important">The call <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">(float *)xpMat->matrix()</code> is simply telling C++ to interpret the stored memory as a float, so it’s simply breaking up the stored binary data into float-sized chunks instead of double-sized chunks, so you get nonsense numbers. To store as a float, you would have to cast <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">double_bigmat</code> to a <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">float</code> type, which I believe makes a new copy of the object after casting each value, so would defeat the purpose. Also big.matrix objects in R only support <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">char</code>, <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">short</code>, <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">int</code>, and <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);border-radius:3px;display:inline;background-color:rgb(248,248,248)">double</code> as the underlying storage type (see help(“big.matrix”, “bigmemory”)), so you wouldn’t be able to access the float matrix from R as a big.matrix (without casting it back to a double) anyway.</p><p style="margin:1.2em 0px!important">Regards,</p><p style="margin:1.2em 0px!important">Scott</p>
<div title="MDH:SGkgWXVlLDxicj48YnI+VGhlIGNhbGwgYChmbG9hdCAqKXhwTWF0LSZndDttYXRyaXgoKWAgaXMg
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