How to rotate x-axis tick labels in Pandas barplot

With the following code:

    import matplotlib
    matplotlib.style.use('ggplot')
    import matplotlib.pyplot as plt
    import pandas as pd

    df = pd.DataFrame({ 'celltype':["foo","bar","qux","woz"], 's1':[5,9,1,7], 's2':[12,90,13,87]})
    df = df[["celltype","s1","s2"]]
    df.set_index(["celltype"],inplace=True)
    df.plot(kind='bar',alpha=0.75)
    plt.xlabel("")

I made this plot:

enter image description here

How can I rotate the x-axis tick labels to 0 degrees?

I tried adding this but did not work:

    plt.set_xticklabels(df.index,rotation=90)

Pass param rot=0 to rotate the xticks:

    import matplotlib
    matplotlib.style.use('ggplot')
    import matplotlib.pyplot as plt
    import pandas as pd

    df = pd.DataFrame({ 'celltype':["foo","bar","qux","woz"], 's1':[5,9,1,7], 's2':[12,90,13,87]})
    df = df[["celltype","s1","s2"]]
    df.set_index(["celltype"],inplace=True)
    df.plot(kind='bar',alpha=0.75, rot=0)
    plt.xlabel("")
    plt.show()

yields plot:

enter image description here

From: stackoverflow.com/q/32244019