Column addition in based on condition of another column using R -

i have data frame mydata follows,

 id ts        tb    tc   1 1.7360     -1    0   2 1.7302     -1    0.254   3 1.7244      0    0.624   4 1.7232      0    0.254   5 1.7208      0    1.25   6 1.7208      0    0   7 1.7208      0    0   8 1.7023      0    0   9 1.6814      0    0  10 1.6768      1    0  11 1.6746      0    6.25  12 1.6503      0    0.2547  13 1.6258      0    0.987  14 1.6190      0    0.3654  15 1.6154      0    0.6251  16 1.6258      0    0.369  17 1.6397      0    0  18 1.6443      0    0  19 1.6491      0    0  20 1.6503      0    0 

now need add/subtract values of ts , tc , create new column tsc condition if there -1 in column tb tsc == ts + tc until there +1 or -1 in tb, else if there 1 in column tb tsc == ts - tc until there +1 or -1 in tb. there possibilities of having 0 @ begining of data frame in column b tsc == ts +tc.

below final result

 id       ts       tb     tc      tsc  1  1.73602       -1    0       1.736020823  2  1.73023       -1    0.254   1.984238239  3  1.72445        0    0.624   2.348455656  4  1.72326        0    0.254   1.977269484  5  1.72089        0    1.25    2.970897142  6  1.72089        0    0       1.720897142  7  1.72089        0    0       1.720897142  8  1.70236        0    0       1.70236322  9  1.68145        0    0       1.681456955 10  1.67686        1    0       1.676860542 11  1.67463        0    6.25    4.575363528 12  1.65031        0    0.2547  1.395619965 13  1.62585        0    0.987   0.638855188 14  1.61903        0    0.3654  1.253634704 15  1.61547        0    0.6251  0.990376191 16  1.62585        0    0.369   1.256855188 17  1.63979        0    0       1.639792697 18  1.64438        0    0       1.64438911 19  1.64913        0    0       1.649133794 20  1.65031        0    0       1.650319965 

by constructing vector of +1 adding , -1 subtracting easy. how construct that?

first constructing vector replacing zeroes previous non-zero. using rle can construct vector of how many times -1, 1, or 0 appears, , replace zeroes previous non-zero, inverse , vector of 1 , -1 only.

stick -1 on start satisfy "if starts zero, subtract" condition:

> rx = rle(c(-1,mydata$tb)) 

now see zeroes are:

> wz = which(rx$values==0) 

set zeroes whatever previous values were.

> rx$values[wz]=rx$values[wz-1] 

now expand vector of 1 , -1, chopping off first rid of -1 started with. also, make +1 adding , -1 subtracting:

> mydata$tbop = -inverse.rle(rx)[-1] 

then operation:

> mydata$tsc=mydata$ts + mydata$tbop*mydata$tc > mydata     id     ts tb     tc tbop     tsc  1:  1 1.7360 -1 0.0000    1  1.7360  2:  2 1.7302 -1 0.2540    1  1.9842  3:  3 1.7244  0 0.6240    1  2.3484  4:  4 1.7232  0 0.2540    1  1.9772  5:  5 1.7208  0 1.2500    1  2.9708  6:  6 1.7208  0 0.0000    1  1.7208  7:  7 1.7208  0 0.0000    1  1.7208  8:  8 1.7023  0 0.0000    1  1.7023  9:  9 1.6814  0 0.0000    1  1.6814 10: 10 1.6768  1 0.0000   -1  1.6768 11: 11 1.6746  0 6.2500   -1 -4.5754 12: 12 1.6503  0 0.2547   -1  1.3956 13: 13 1.6258  0 0.9870   -1  0.6388 14: 14 1.6190  0 0.3654   -1  1.2536 15: 15 1.6154  0 0.6251   -1  0.9903 16: 16 1.6258  0 0.3690   -1  1.2568 17: 17 1.6397  0 0.0000   -1  1.6397 18: 18 1.6443  0 0.0000   -1  1.6443 19: 19 1.6491  0 0.0000   -1  1.6491 20: 20 1.6503  0 0.0000   -1  1.6503 

probably best write testable function operator:

top <- function(x){  rx = rle(c(-1,x))  wz = which(rx$values==0)  rx$values[wz] = rx$values[wz-1]  -inverse.rle(rx)[-1] } 

then can check simple examples:

> top(0) # add [1] 1 > top(-1) # add [1] 1 > top(1) # subtract [1] -1  > top(c(0,-1,1,-1,0,0,0)) [1]  1  1 -1  1  1  1  1   # add, add, sub, add, add, add, add  > top(mydata$tb) [1]  1  1  1  1  1  1  1  1  1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 

then solution one-liner:

> mydata$tsc = mydata$ts + top(mydata$tb) * mydata$tc