R: ggplot2 x axis prints as continuos, but needed as discreate -

my data:

structure(list(year = structure(1:10, .label = c("1980", "1981",  "1982", "1983", "1984", "1985", "1986", "1987", "1988", "1989" ), class = "factor"), lupas = c(1185, 822, 1340, 853, 3018, 1625,  966, 1505, 1085, 1754)), .names = c("year", "lupas"), row.names = c(na,  -10l), class = c("tbl_df", "tbl", "data.frame"), drop = true) 

i've group data group_by dplyr.

str(df1) classes ‘tbl_df’, ‘tbl’ , 'data.frame':   10 obs. of  2 variables:  $ year : factor w/ 10 levels "1980","1981",..: 1 2 3 4 5 6 7 8 9 10  $ lupas: num  1185 822 1340 853 3018 ...  - attr(*, "drop")= logi true 

i'm trying plot graph of years, , "lupas" each year. time series graph.

this code, gives error:

ggplot(df1,    aes(x = year, y = lupas)) + geom_line()   geom_path: each group consist of 1 observation. need adjust group aesthetic? 

and graph:

after reading thread: ggplot2 each group consists of 1 observation

i've changed code to:

ggplot(df1,    aes(x = year, y = lupas)) + geom_line(position=position_dodge(.1)) 

now message:

ymax not defined: adjusting position using y instead geom_path: each group consist of 1 observation. need    adjust group aesthetic? 

maybe helps:

library(ggplot2) p <- ggplot(df1, aes(x = year, y = lupas, group = 1)) +       geom_point(color = "black") + geom_line(color = "blue") 

edit

to display specific ticks on x-axis 1 can use scale_x_discrete() in combination breaks:

p <- ggplot(df1, aes(x = year, y = lupas, group = 1)) +     geom_point(color = "black") + geom_line(color = "blue") +   scale_x_discrete(breaks = c("1980", "1985", "1989"))