如何从熊猫数据框中找到最小和最大AND对应的x值？

Question

I want to be able to find the min and max of a pandas data frame AND the corresponding X-value. As of now, I just have it find the Y-Value max and min, but I can't figure out how to provide a corresponding X-Value. What can I do to get this corresponding value?

So this finding of the min and max is included in a loop for writing an excel file and I want to eventually write out them max or min values in the excel file as well. I have tried doing this function to give the corresponding values

maxVal = dfspectra.loc[dfspectra['Current (mA)'].idxmax()] minVal = dfspectra.loc[dfspectra['Current (mA)'].idxmin()]

This did not work and only gives me NaN or says that the data frame cannot be callable

Here is the initial introduction of the data frame:

for filename in filestoprocess:
    baseName=os.path.basename(os.path.basename(filename))
    dfspectra=pd.read_csv(filename, skiprows = 1, delimiter =        "\s+|\t+|\0+", header = None, names = ['Potential (V)','Current (mA)'],     engine='python', skipfooter=1,skipinitialspace=True)
    fig, ax = plt.subplots()
    ax.plot(dfspectra['Potential (V)'],dfspectra['Current (mA)'],     "ok")
    ax.set(xlabel='Potential (V)', ylabel='Current (mA)', title='CV Data')

And here is my attempt of finding the max/min and corresponding x-value:

 ymax = np.max(dfspectra['Current (mA)'])
 ymin = np.min(dfspectra['Current (mA)'])
 maxVal = dfspectra.loc[dfspectra['Current (mA)'].idxmax()]
 minVal = dfspectra.loc[dfspectra['Current (mA)'].idxmin()]

When I put min or maxVal into the console, it gives my full data frame and when I try maxVal(dfspectra['Current (mA)'], it says that the data frame is not callable. I thought that the numpy function finds the Y-value while the loc function gives the X-value.

Answer 1

Try this -

indx_max = np.argmax(dfspectra['Current (mA)'])
x_max = dfspectra.iloc[indx_max]

The first statement finds the index that contains the maximum value in column Current (mA) in your dfspectra . The second statement returns the row corresponding to the index from first row. For minima, use np.argmin .

indx_min = np.argmin(dfspectra['Current (mA)'])
x_min = dfspectra.iloc[indx_min]