first time use plot - I get empty graph

[korenron]

Hello,
I want to show variable in a graph , I don't have "x" only the value of y
so I thought to create an int for numbers of time I get the speed and increase it every time

I will explain
I'm reading speed senor and I want to create a speed graph
the function read the data from a known file , return and print it - this part works without any problems.
this is what I have

import matplotlib.pyplot as plt

t = 0
def GetDataFunction()
    global t
    Speed = GetData()
    print(f"Speed: {Speed} Km/h ")
    plt.plot(t, float(Speed))
    t += 1

GetDataFunction()

plt.show()

what did I miss?



***
I have try to make it even more simple

import matplotlib.pyplot as plt
 
t = 0
Speed = [0, 1, 3, 50, 60, 22, 30]

def Function():
    global t
    while t < len(Speed):
      print(t, '-', Speed[t])
      plt.plot(t, Speed[t])
      t += 1
    
Function()

but I get the same result - empty graph
I can see the max value is:
Y - 60
X - 6
so something is right :-)

Thanks ,