with Python, pandas and matplotlib

import serial
import pandas as pd
import matplotlib.pyplot as plt

ser = serial.Serial('COM4', '115200', timeout = 0.5)
print(ser.name)
serialCmd = b'WIN\r'
readSize = 17
loop = True
freq = ""
win = 0
data = []

try:
    while (loop == True):
        ser.write(serialCmd)
        result = ser.read(readSize)
        res = str(result)
        if (len(res) > 15):
            i = res.find(",")
            j = res.find(",", i + 1)
            if ((i != -1) and (j != -1)):
                freq = res[j + 1:j + 9]
                win = int(res[i + 1:i + 4])
                i = -1
                b = False
                for x in data:
                    i = i + 1
                    if (x[0] == freq):
                        data[i][1] = win
                        b = True
                        break
                if (b == False):
                    data.append([freq, win])
except KeyboardInterrupt:
    loop = False
ser.close()

df = pd.DataFrame(data, columns = ['Frequency', 'Window voltage'])
df = df.sort_values('Frequency')
plt.xlabel("Frequency")
plt.ylabel("Window voltage")
plt.bar('Frequency', 'Window voltage', data = df, width = 0.5)
plt.show()

https://i.ibb.co/kcsdDcP/plot.jpg