Analog input oscillating between 0 and 1023

i've connected analog input a1 -> 1m ohm resistor -> ground.

when touch resistor, @ point connected a1, following. what happening? 

this code:

code: [select]


while (true) {
serial.println(analogread(1));
delay(1);
}


gives me following output:

code: [select]


0
0
0
0
0
0
0
0
0
145
502
1023
1023
1023
1023
0
0
0
0
0
0
0
0
0
0
158
792
1023
1023
1023
1023
0
0
0
0
0
0
0
0
0
0
167
996
1023
1023
1023
1023

what seeing natural.
the input impedance of analog input high.
the input float or take on voltage of whatever connected it.

google: arduino analog input floating.

place 10k resistor on input gnd.

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