[R] Lines in a line graph not visible when values are identical

[Bob Green]

Thanks Rui,

Much appreciated. Regarding why I spelt out 
millimetres, I seldom use them as a measurement 
so it was mostly for that reason and because the 
data was in an Excel spreadsheet.

To get a more direct comparison, I create a panel 
of four bargraphs, one for each parameter by year.

Regards

Bob

  At 01:27 AM 10/9/2026, Rui Barradas wrote:
>Hello,
>
>What if instead of colors, you facet the plot by Year?
>
>
>ggplot(DF, aes(x = Parameter, y = Millimetres, group = Year)) +
>   geom_line(linewidth = 1) +
>   geom_point(size = 2) +
>   labs(
>     title = "Parameters by Year",
>     x = "Parameter",
>     y = "Millimetres ($)"
>   ) +
>   facet_wrap(~ Year) +
>   theme_minimal()
>
>
>Also, the data in dput format.
>
>DF <-
>structure(list(Parameter = structure(c(1L, 2L, 3L, 4L, 1L, 2L,
>3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L,
>3L, 4L, 1L, 2L, 3L, 4L, 1L, 2L, 3L, 4L), levels = c("Tail", "Tail_b",
>"Nose_b", "Nose"), class = "factor"), Millimetres = c(0, 0, 20.3,
>74.9, 0, 0, 14, 63.7, 11.2, 2.8, 16.3, 72.6, 0, 0, 17.1, 72.5,
>11.3, 2.9, 16.9, 74.7, 28.1, 4.9, 6.8, 37.7, 25.9, 5.2, 11.2,
>68.1, 30.2, 6.35, 15.1, 76.2), Year = c("2010-2012", "2010-2012",
>"2010-2012", "2010-2012", "2014", "2014", "2014", "2014", "2016",
>"2016", "2016", "2016", "2023", "2023", "2023", "2023", "2024",
>"2024", "2024", "2024", "2025C", "2025C", "2025C", "2025C", "2025B",
>"2025B", "2025B", "2025B", "2026", "2026", 
>"2026", "2026")), row.names = c("1",
>"2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13",
>"14", "15", "16", "17", "18", "19", "20", "21", "22", "23", "24",
>"25", "26", "27", "28", "29", "30", "31", "32"), class = "data.frame")
>
>Bob Green via R-help <r-help using r-project.org> escreveu (quinta,
>8/10/2026 Ã (s) 11:19):
> >
> > Hello,
> >
> > I'm pretty rusty using R but wanted to compare
> > four parameters measured in mm, in terms of the year an object was created.
> >
> > My problem is that where there are identical
> > values, only one line is produced. For example,
> > for the first parameter "tail",only five of a 
> possible eight lines are visible.
> >
> > The code and full dataset are below. I considered
> > making trivial differences to identical values of
> > a parameter to create difference,but no doubt
> > there are more elegant or sophisticated options.
> >
> > Any advice is appreciated,
> >
> > Bob
> >
> > library(ggplot2)
> > library(tidyr)
> > library(readxl)
> > DF <- read_excel("C:/Files/DataLong.xlsx")
> > DF
> >
> >
> > DF$Parameter <- factor(DF$Parameter, levels =
> > c("Tail", "Tail_b", "Noseb", "Nose"))
> >
> >
> > ggplot(DF, aes(x = Parameter, y = 
> Millimetres, color = Year, group = Year)) +
> >    geom_line(linewidth = 1) +
> >    geom_point(size = 2) + labs(title =
> > "Parameters by Year", x = "Parameter", y = "Millimetres ($)") +
> >    theme_minimal()
> >
> > ##Data
> >
> >
> > # A tibble: 32 × 3
> >     Parameter Millimetres Year
> >     <fct>           <dbl> <chr>
> >   1 Tail             0    2010-2012
> >   2 Tail_b           0    2010-2012
> >   3 Nose_b          20.3  2010-2012
> >   4 Nose            74.9  2010-2012
> >   5 Tail             0    2014
> >   6 Tail_b           0    2014
> >   7 Nose_b          14    2014
> >   8 Nose            63.7  2014
> >   9 Tail            11.2  2016
> > 10 Tail_b           2.8  2016
> > 11 Nose_b          16.3  2016
> > 12 Nose            72.6  2016
> > 13 Tail             0    2023
> > 14 Tail_b           0    2023
> > 15 Nose_b          17.1  2023
> > 16 Nose            72.5  2023
> > 17 Tail            11.3  2024
> > 18 Tail_b           2.9  2024
> > 19 Nose_b          16.9  2024
> > 20 Nose            74.7  2024
> > 21 Tail            28.1  2025C
> > 22 Tail_b           4.9  2025C
> > 23 Nose_b           6.8  2025C
> > 24 Nose            37.7  2025C
> > 25 Tail            25.9  2025B
> > 26 Tail_b           5.2  2025B
> > 27 Nose_b          11.2  2025B
> > 28 Nose            68.1  2025B
> > 29 Tail            30.2  2026
> > 30 Tail_b           6.35 2026
> > 31 Nose_b          15.1  2026
> > 32 Nose            76.2  2026
> >
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