r - table() generating NAs when there are no NAs in the underlying data -


i want generate column of counts of particular variable. easiest way seems using table(). reasonably small amounts of data, there seems no problem. 

a <- data.frame(a1 = sample(1:1000, 100000, replace = true)) b <- data.frame(b1 = sample(1:1000, 100000, replace = true)) c <- cbind(a, b) c$countc <- table(as.factor(c$a1))[c$a1]  summary(c$countc) min. 1st qu.  median    mean 3rd qu.    max.   65      94     101     101     108     132

however, if i'm building table larger set (note i'm sampling 1:10k, rather 1:1k), generates nas, despite there being no nas in data i'm building table from:

a <- data.frame(a1 = sample(1:10000, 100000, replace = true)) b <- data.frame(b1 = sample(1:10000, 100000, replace = true)) c <- cbind(a, b) c$countc <- table(as.factor(c$a1))[c$a1]  summary(c$a1) min. 1st qu.  median    mean 3rd qu.    max.    1    2512    5005    5008    7502   10000   summary(c$countc) min. 1st qu.  median    mean 3rd qu.    max.    na's  1.00    8.00   10.00   10.18   12.00   25.00       7

the problem not occur if data not in data-frame. 

a <- sample(1:10000, 1000000, replace = true) summary(table(as.factor(a))[a]) min. 1st qu.  median    mean 3rd qu.    max.  57      94     101     101     108     144

does know reason why?

after installing data.table package , doing preliminaries...

require(data.table) n0<- 1e5 n <- 1e6 dt <- data.table(a1 = sample(1:n0, n, replace = true),b1 = sample(1:n0, n, replace = true))

this trick.

setkey(dt,a1) dt[     dt[,.n,by=a1],     countc:=n ]

when access data.table dt[i,j], can select rows i , else j, in data.frames.

dt[,.n,by=a1] selects rows (since i blank) , counts rows each "a1" using special variable .n.

after setting column "a1" key dt, can pass data.table -- in case dt[,.n,by=a1] -- in i merge information in latter data.table. in j, create new column in dt using countc:=n. 3 vignettes on data.table's cran page place start learning more how works.

the question @ hand. oh, think see original problem was. suppose unique(x)=c(1,2,4). if try table(x)[x], trying access table(x)[1], table(x)[2] , table(x)[4]. last 1 undefined since length of table 3. r returns na when access indices greater length of vector. example, @ (1:3)[4].

in case, if missing unique values in 1:n0 not @ top, see nas.


Comments

Post a Comment

Popular posts from this blog

.htaccess - First slash is removed after domain when entering a webpage in the browser -

sometimes when hit address of webpage in browser, removes first slash after domain. examples: www.mywebsite.com/scripts/script_6.php -> trying load www.mywebsite.comscripts/script_6.php www.mywebsite.com/test.php -> trying load www.mywebsite.comtest.php after entering again, loads page. a .htaccess settings must wrong: rewritebase / errordocument 404 http://www.mywebsite.com/oops.php errordocument 401 /notallowed.php rewriteengine on # turn on rewriting engine #gzip <ifmodule mod_deflate.c> addoutputfilterbytype deflate text/text text/html text/plain text/xml text/css application/x- javascript application/javascript </ifmodule> #end gzip rewritecond %{http_host} ^mywebsite\.com rewriterule ^(.*)$ http://www.mywebsite.com$1 [r=permanent,l] directoryindex index6.php rewriterule ^termsofuse/?$ termsofuse.php [nc,l] # handle requests "adpolicy" rewriterule ^privacy-policy/?$ privacy-policy.php [nc,l] # handle requ...
Read more

Automatically create pages in phpfox -

i have array of information of places , wanna use them create multiple pages in phpfox site. first tried manually insert data in phpfox database (in tables of phpfox_pages , phpfox_pages_text ). the page shown in site when opening it's link, site says: the page looking cannot found. do know other tables should manipulate make work? or know plugin phpfox same? thanks, solved ( @purefan guide): "pages" has user if take @ phpfox_user table, you'll found out how fetch new records on that. there 2 ambiguous fields in table ( password & password_salt ). can use script create values fields: <?php function generaterandomstring() { $length = 164; $characters = '-_0123456789abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz'; $randomstring = ''; ($i = 0; $i < $length; $i++) { $randomstring .= $characters[rand(0, strlen($characters) - 1)]; } return $randomstring; } $ssalt = '';...
Read more

c# - Farseer ContactListener is not working -

i'm using farseer in xna project, have trouble contactlistener. created class contactlistener these 2 error messages , don't know how fix problems. the type or namespace name 'contactlistener' not found (are missing using directive or assembly reference?) the type or namespace name 'contactimpulse' not found (are missing using directive or assembly reference?) what wrong contactlistener class? class mycontactlistener: contactlistener { void begincontact(contact contact) { /* handle begin event */ } void endcontact(contact contact) { /* handle end event */ } void presolve(contact contact, ref manifold oldmanifold) { fixture fixturea = contact.fixturea; fixture fixtureb = contact.fixtureb; if (fixtureb.collisioncategories == category.cat10) { contact.enabled = false; } } void postsolve(contact contact, ref contactimpulse impulse) { /* handle post-solve event */ } }...
Read more