r - odd behavior of print within mapply -


i seeing unexpected behavior (to me anyway) when print() included side effect in function wrapped in mapply().

for example, works expected (and yes know it's not how add vectors):

mapply(function(i,j) i+j, i=1:3, j=4:6) # returns [1] 5 7 9

and this:

mapply(function(i,j) paste(i, "plus", j, "equals", i+j), i=1:3, j=4:6)  # returns [1] "1 plus 4 equals 5" "2 plus 5 equals 7" "3 plus 6 equals 9"

but doesn't:

mapply(function(i,j) print(paste(i, "plus", j, "equals", i+j)), i=1:3, j=4:6) # returns: # [1] "1 plus 4 equals 5" # [1] "2 plus 5 equals 7" # [1] "3 plus 6 equals 9" # [1] "1 plus 4 equals 5" "2 plus 5 equals 7" "3 plus 6 equals 9"

what's going on here? haven't used mapply() in while, maybe no-brainer... i'm using r version 3.4.0.

print both prints argument , returns value.

p <- print("abc") # [1] "abc" p # [2] "abc"

so each element gets printed, vector of stuff gets returned (and printed). try e.g. invisible(mapply(...)) or m <- mapply(...) comparison.

fwiw cat() returns null ...


Comments

Post a Comment

Popular posts from this blog

Is there a better way to structure post methods in Class Based Views -

i'm using class based views in django , never specify url in ajax calls , omit action parameter in form because know these requests go through post method of class based view. notice view - profile page make many requests depending on user updating on page - post method become convoluted , if/else mess example: def post(self, request, *args, **kwargs): # handle user changing available date if request.post.get('availabledate') != none: self.updateavailabledate(request) return jsonresponse({'result':'success'}) if request.post.get('newprojectname') != none: creative_user = creativeuserprofile.objects.get(id = request.user.id) project = project.create_project(creative_user, request.post['newprojectname']) project.save() return jsonresponse({'projectid': project.id }) if request.post.get('projectimage') != none , request.files['file']: proj...
Read more

performance - Why is XCHG reg, reg a 3 micro-op instruction on modern Intel architectures? -

i'm doing micro-optimization on performance critical part of code , came across sequence of instructions (in at&t syntax): add %rax, %rbx mov %rdx, %rax mov %rbx, %rdx i thought had use case xchg allow me shave instruction , write: add %rbx, %rax xchg %rax, %rdx however, dimay found agner fog's instruction tables , xchg 3 micro-op instruction 2 cycle latency on sandy bridge, ivy bridge, broadwell, haswell , skylake. 3 whole micro-ops , 2 cycles of latency! 3 micro-ops throws off 4-1-1-1 cadence , 2 cycle latency makes worse original in best case since last 2 instructions in original might execute in parallel. now... cpu might breaking instruction micro-ops equivalent to: mov %rax, %tmp mov %rdx, %rax mov %tmp, %rdx where tmp anonymous internal register , suppose last 2 micro-ops run in parallel latency 2 cycles. given register renaming occurs on these micro-architectures, though, doesn't make sense me done way. why wouldn't register renamer ...
Read more

c# - Asp.net web api : redirect unauthorized requst to forbidden page -

im trying redirect unauthorized request forbidden page instead i'm getting forbidden page in response body , how can fix ? here's startup class : app.createperowincontext(storecontext.create); app.createperowincontext<applicationusermanager>(applicationusermanager.create); app.createperowincontext<applicationsigninmanager>(applicationsigninmanager.create); app.usecookieauthentication(new cookieauthenticationoptions { authenticationtype = defaultauthenticationtypes.applicationcookie, expiretimespan = timespan.fromdays(30), }); app.useexternalsignincookie(defaultauthenticationtypes.externalcookie); app.usetwofactorsignincookie(defaultauthenticationtypes.twofactorcookie, timespan.fromminutes(5)); app.usetwofactorrememberbrowsercookie(defaultauthenticationtypes.twofactorrememberbrowsercookie); the method im trying reach : [httpget] [authorize(roles = "admin")] public string getcurrentusername() { return userman...
Read more