Nested ifelse() within for() loop...syntax error?

Question

Quite a specific question...but here it goes.

I have a vector of data indicating thermal change, and from it would like to know whether something has been switched 'ON' or 'OFF'. This something always starts 'OFF'. A threshold of +1.5 degrees indicates it has been switched 'ON', and stays on until a threshold of -1.5 degrees indicates it has been switched 'OFF' again, reaching high or low plateaus in between with much smaller +/- change. I have a numeric vector of positive and negative values that I would like to turn into a character or factor with levels 'ON' and 'OFF' in the appropriate places.

Using this:

    > Data$delta
    [1]  0.02  0.00  0.04 -0.06 -0.06 -0.02  0.01  0.31  0.22  0.21 -0.09 -0.02  0.03  0.02  0.01
    [16]  0.00  0.02  0.03  0.03  0.04  0.04  0.01  0.00  0.01  0.02  0.05  0.04  0.04  0.01  0.04
    [31]  0.02  0.01 -0.03  0.00  0.03  0.03  0.03  0.04  0.04  0.02  0.02  0.01  0.02 -0.02 -0.01
    [46] -0.03  0.01  0.03  0.37  0.14  0.04 -0.34 -0.15 -0.07  0.00  0.01  0.29  0.03  0.26 -0.12
    [61]  0.05 -0.02 -0.03  0.10 -0.11 -0.01 -0.07 -0.03 -0.01  0.01  0.30  0.12  0.05 -0.25 -0.06
    [76] -0.04 -0.04 -0.07 -0.02  0.01  0.04  0.02  0.03 -0.07 -0.12 -0.18 -0.12 -0.08 -0.05 -0.04
    [91]  0.34  2.99  4.29  5.00  1.83 -0.51 -1.63 -0.33  2.62 -0.38

I create an empty vector to receive the for() loop output and insert 'OFF' as switch is always starting with 'OFF'

    > Data$switch<- as.character(NA)
    > Data$switch<-as.character(c("OFF",Data$switch[2:(length(Data$switch))]))
    > head(Data$switch
    [1] "OFF" NA    NA    NA    NA    NA

I then create my nested ifelse() for() loop, accounting for the fact row 1 of Data$switch is already complete...

    > for(i in (2:(length(Data$delta))))
    {  ifelse(Data$switch[1:((length(Data$switch))-1)] == "OFF", 
       (ifelse (Data$delta[i] < 1.5 , Data$switch[i] <- "OFF", Data$switch[i] <- "ON" )),
       (ifelse (Data$delta[i] > {-1.5} , Data$switch[i] <- "ON", Data$switch[i] <- "OFF")))
    }

Which returns...

> Data$switch
[1] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[16] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[31] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[46] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[61] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[76] "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF" "OFF"
[91] "OFF" "ON"  "ON"  "ON"  "ON"  "ON"  "OFF" "ON"  "ON"  "ON"

Which all appears fine...apart from value 98, which should not have switched to 'ON' with delta only '-0.33'. On a larger data set these seem to be regular false change from OFF to ON at values <1.5? I've tried the syntax again in multiple forms but these are worse not better. Can anyone help identify the problem please? Data$delta is a numeric vector.

values 97 and 98 have a flag : -1.63 *-0.33* and will be seen as characters. I don't see a as.numeric in your code, but it will set these values to NA. — Henk
– Henk, Commented Jun 10, 2014 at 14:25
@Henk ...sorry the flag is not a flag, I was trying to put value 98 in bold font to illustrate the point. I will change this — Roasty247
– Roasty247, Commented Jun 10, 2014 at 14:34

MrFlick · Accepted Answer · 2014-06-10 14:57:40Z

1

OK. Here are your delta values in a more copy/paste friendly format

delta <- c(0.02, 0, 0.04, -0.06, -0.06, -0.02, 0.01, 0.31, 0.22, 0.21, 
-0.09, -0.02, 0.03, 0.02, 0.01, 0, 0.02, 0.03, 0.03, 0.04, 0.04, 
0.01, 0, 0.01, 0.02, 0.05, 0.04, 0.04, 0.01, 0.04, 0.02, 0.01, 
-0.03, 0, 0.03, 0.03, 0.03, 0.04, 0.04, 0.02, 0.02, 0.01, 0.02, 
-0.02, -0.01, -0.03, 0.01, 0.03, 0.37, 0.14, 0.04, -0.34, -0.15, 
-0.07, 0, 0.01, 0.29, 0.03, 0.26, -0.12, 0.05, -0.02, -0.03, 
0.1, -0.11, -0.01, -0.07, -0.03, -0.01, 0.01, 0.3, 0.12, 0.05, 
-0.25, -0.06, -0.04, -0.04, -0.07, -0.02, 0.01, 0.04, 0.02, 0.03, 
-0.07, -0.12, -0.18, -0.12, -0.08, -0.05, -0.04, 0.34, 2.99, 
4.29, 5, 1.83, -0.51, -1.63, -0.33, 2.62, -0.38)

Here's one way to get the data you want. First, I track when "on" and "off" flags occur and set the initial flag to off (off=1, on=2)

flags <- ifelse(delta< -1.5, 1, ifelse(delta>1.5, 2, NA))
flags[1]<-1

Now this vector has a lot of missing values. What i need to do is just carry the last value forward. I'll do that with

state <- Reduce(function(a,b) {ifelse(is.na(b),a,b)}, flags, accumulate=T)
c("OFF","ON")[state]

answered Jun 10, 2014 at 14:57

MrFlick

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1 Comment

alexis_laz Over a year ago

+1 for Reduce but, since you end up in Reduce, avoiding ifelses with something like

Reduce(function(i1, i2) {if(i2 >= 1.5) return("ON"); if(i2 <= -1.5) return("OFF"); return(i1)}, c("OFF", as.list(delta[-1])), acc = T)

looks valid, unless I'm missing something.

Roasty247 · Accepted Answer · 2014-06-23 13:36:50Z

0

    > for(i in (2:(length(Data$delta))))
{  ifelse(Data$switch[i-1] == "OFF", 
   (ifelse (Data$delta[i] < 1.5 , Data$switch[i] <- "OFF", Data$switch[i] <- "ON" )),
   (ifelse (Data$delta[i] > {-1.5} , Data$switch[i] <- "ON", Data$switch[i] <- "OFF")))
}

I believe I solved the problem! Thanks for other solutions people

edited Jun 23, 2014 at 13:36

answered Jun 11, 2014 at 12:33

Roasty247

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