Creating a plot using data imported from Excel

I am trying to create plots starting from values that I have in an Excel spreadsheet. The values of interest are contained in three rows, which I will call 1, 2, and 3 for the sake of this discourse. The thing is, even if I get the data into Mathematica, it treats the data as if it were a list of y values.

Is there a command to specify that the values in row 1 are values of the independent variable x? Is there a way to plot the values in rows 2 and 3 against row 1 in the same plot?

I'll guess your data looks like

data = {{1, 2, 3, 4}, {10, 19, 28, 41}, {11, 21, 30, 39}};

where the first bracket is the first row, and the other two brackets are the other rows. You could then get the plot you're looking for as

ListPlot[Transpose@data[[{1, #}]] & /@ {2, 3}]

where you can fill in whichever rows you're interested in for the {2,3}.

Assuming you are able to get the data into Mathematica and that I understand your question correctly, you can parse the dataset directly in any discrete plotting function.

Making up some data:

x = Subdivide[0, 1, 99];
y = RandomReal[{0, 1}, 100];
z = RandomReal[{0, 1}, 100];

Or, if you import the data as a single set:

data = {x, y, z};

You can plot using either

ListLinePlot[MapThread[Flatten@*List, {x, #}] & /@ {y, z}]

or

ListLinePlot[MapThread[Flatten@*List, {data[], #}] & /@ data[[2 ;;]]]

to obtain the plot 