[R] scatter plot of numerical variables against different sample ids

[Maria Lathouri]

Dear all
I know that my question is very simple but although I tried to find an answer online, I couldn't and I am stuck. 
I have a dataset of three numerical variables measured in different samples ID. Something like this:
Sample        Cu        Zn        MnM1               1          5          10M2               2.5       11          8M3              1.15      11         12  M4                2         4          30M5                8        15         35
I would like to plot these variables (Cu, Zn, Mn) (in y-axis) against the Sample ID (in x-axis) in a scatter plot with lines as I want to see how they change in the samples.
I tried using the command>plot(Sample, Cu, type="l", lty=1, col="red")
but I wouldn't get a line. Actually, I would get some small horizontal lines in each point. I tried to use type="p" but I would get the same thing. 
I would very much appreciate if you could help me on that. Apparently, I am missing something. 
Thank you in advance. 
Kind regards,Maria
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