R: lines() and points() solution in multiple plots separated by groups

[redshoe]

I am relatively new to R and I am trying to do the following.

I am looking for a way to generate single plots defined by group (based on the ID).

My goal: Generally I am looking for a way to always plot row based points in the following pattern

- starting point: REFERENCE_YEAR/REFERENCE_YEAR_VALUE to end point: SURVEY_YEAR/SURVEY_YEAR_VALUE and connect these points by a line

My sample data.frame looks like this:

xy <- data.frame(NAME=c("NAME1","NAME1","NAME1","NAME2","NAME2","NAME2"),ID=c(87,87,87,199,199,199), SURVEY_YEAR=c(1986,1994,1999,1909,1924,1927), REFERENCE_YEAR=c(1984,1986,1984,1899,1909,1924), VALUE_SURVEY_YEAR=c(20,50,-15,-70,-80,-100),VALUE_REFERENCE_YEAR=c(75,25,-90,-8,-55,-10))

xy
       NAME  ID SURVEY_YEAR REFERENCE_YEAR VALUE_SURVEY_YEAR VALUE_REFERENCE_YEAR
1 NAME1  87        1986           1984                20                   75
2 NAME1  87        1994           1986                50                   25
3 NAME1  87        1999           1984               -15                  -90
4 NAME2 199        1909           1899               -70                   -8
5 NAME2 199        1924           1909               -80                  -55
6 NAME2 199        1927           1924              -100                  -10

In numbers the example for the group plot with ID 87 would be as follows

• For row 1 plot a starting point 1984/75 and end point 1986/20 and these two points should be connected by a line

• Then move on to row 2 and plot starting point 1986/25 and end point 1994/50 and connect the points with a line

• Then move on to row 3 and plot a starting point 1984/-90 and end point 1999/-15 and connect the points with a line.

As this group (defined by ID) is finished now, start with a new graph and repeat the whole procedure with a new plot and a new group (in this case for the group with ID 199).

How I tried to solve this problem:
I tried to reorganise the dataframe by writing REFERENCE_YEAR and SURVEY_YEAR one below the other and reorganised the data into two columns YEAR and VALUE in order to create an xy plot but this didn't result in correct plots as described above.

xy <- reshape(xy, direction="long",
              varying = list(c("SURVEY_YEAR","REFERENCE_YEAR"), c("VALUE_SURVEY_YEAR","VALUE_REFERENCE_YEAR")), 
              v.names=c("YEAR","VALUE"), times = c("SURVEY_YEAR", "REFERENCE_YEAR"))
xy <- xy[with(xy, order(NAME, ID, YEAR,time, id)), ]

After that I am splitting it by group (defined by ID) and I'm plotting it into separate graphs.

ind <- split(x = xy,f = xy[,'ID'])
    plot1 <- function(x) {
      fname <- paste0(x[1, 'ID'], '.png')
      png(fname, width=1679, height=1165, res=150)
      par(mar=c(6,8,6,5))
      plot(x = c(1946, 2014),
           y = range(x$VALUE, na.rm=TRUE),
           type='n',
           main=x[1, 'NAME'])
      points(x[,c('YEAR','VALUE')], type="l", lwd=2)
      points(x[,c('YEAR','VALUE')], type="p", lwd=1, cex=0.7, pch=21, bg='white')
    dev.off()
    }
    plot2 <- function(x) {
      fname <- paste0(x[1, 'ID'], '.png')
      png(fname, width=1679, height=1165, res=150)    
      par(mar=c(6,8,6,5))
      plot(x[,c('YEAR','VALUE')],
           type='n',
           main=x[1, 'NAME'])
    points(x[,c('YEAR','VALUE')], type="l", lwd=2)
    points(x[,c('YEAR','VALUE')], type="p", lwd=1, cex=0.7, pch=21, bg='white')
    dev.off() 
    }

    lapply(ind, function(x) ifelse(any(x$YEAR < 1946 & x$YEAR < 2014), plot2(x), plot1(x)))

Does anyone have an idea how I could solve the above mentioned problem maybe also using lines() and points()? I am looking for a solution in Base R. Any help would be kindly appreciated since I am relatively new to R and I am stuck.

Thank you,
redshoe