switch statement usage

Question

I am a little confused about the switch statement in R   Simply googling the function I get an example as follows   A common use of switch is to branch according to the character value of one of the arguments to a function     gt  centre  lt - function x  type       switch type            mean   mean x             median   median x             trimmed   mean x  trim    1          gt  x  lt - rcauchy 10    gt  centre x   mean     1  0 8760325   gt  centre x   median     1  0 5360891   gt  centre x   trimmed     1  0 6086504   However this just seems to be the same as just having a bunch of if statements designated for each type  Is that all there is to switch    Can someone give me further examples and better applications

User · Answer

In short  yes  But there are times when you might favor one vs  the other  Google  case switch vs  if else   There are some discussions already on SO too  Also  here is a good video that talks about it in the context of MATLAB   http   blogs mathworks com pick 2008 01 02 matlab-basics-switch-case-vs-if-elseif   Personally  when I have 3 or more cases  I usually just go with case switch

User · Answer

Well  timing to the rescue again  It seems switch is generally faster than if statements  So that  and the fact that the code is shorter neater with a switch statement leans in favor of switch     Simplified to only measure the overhead of switch vs if  test1  lt - function type     switch type          mean   1          median   2          trimmed   3     test2  lt - function type     if  type     mean   1  else if  type     median   2  else if  type     trimmed   3    system time  for i in 1 1e6  test1  mean       0 89 secs system time  for i in 1 1e6  test2  mean       1 13 secs system time  for i in 1 1e6  test1  trimmed       0 89 secs system time  for i in 1 1e6  test2  trimmed       2 28 secs   Update With Joshua s comment in mind  I tried other ways to benchmark  The microbenchmark seems the best     and it shows similar timings    gt  library microbenchmark   gt  microbenchmark test1  mean    test2  mean    times 1e6  Unit  nanoseconds            expr  min   lq median   uq      max 1 test1  mean    709  771    864  951 16122411 2 test2  mean   1007 1073   1147 1223  8012202   gt  microbenchmark test1  trimmed    test2  trimmed    times 1e6  Unit  nanoseconds               expr  min   lq median   uq      max 1 test1  trimmed    733  792    843  944 60440833 2 test2  trimmed   2022 2133   2203 2309 60814430   Final Update Here s showing how versatile switch is   switch type  case1 1  case2   case3 2 5  99    This maps case2 and case3 to 2 5 and the  unnamed  default to 99  For more information  try  switch

[r] switch() statement usage

Examples related to r

Examples related to switch-statement