creating scatter plot from data file with missing values (sparse matrix)

Question

I have a data set with multiple columns, where some entries are blank. I want to import and plot this data using tikzpicture. However, the resulting graph looks like some values are repeated. Can anyone see an error or suggest a better approach for what I want to do?

simultation_results.dat::
dest    ds1     ds2         ds3       ds4
5       2       43                    5
6       32                  34        9
7       7       125         54        3
8       98                  4         3

Here is my code so far:

\begin{tikzpicture}
\begin{axis}
\addplot+ [ only marks,
        scatter,
        mark=x] table [x=dest, y=ds1] {simulation_results.dat};
\addplot+ [ only marks,
        scatter,
        mark=+] table [x=dest, y=ds2] {simulation_results.dat};
\addplot+ [ only marks,
        scatter,
        mark=-] table [x=dest, y=ds3] {simulation_results.dat};
\addplot+ [ only marks,
        scatter,
        mark=triangle*] table [x=dest, y=ds4] {simulation_results.dat};

\end{axis}
\end{tikzpicture}

Here is the resulting plot. Notice that some data points are repeated horizontally (they should not be)

Answer 1

Finally, I used a filter and back-filled the empty columns with 0. Since 0 will not occur in my dataset, I ignore those values in the plot.

Solution found here: How to hide empty (value 0) ybars with pgfplots?

simultation_results.dat::
dest    ds1     ds2         ds3       ds4
5       2       43          0         5
6       32      0           34        9
7       7       125         54        3
8       98      0           4         3


\addplot+ [ 
    y filter/.expression={y==0 ? nan : y*1000000},
    only marks,
    scatter,
    mark=x] table [x=dest, y=ds1] {simulation_results.dat};