[SOLVED] Simple input impedance simulation

[neddie]

Hi to all.
I'm trying to simulate input impedance in LTSpice.
I've got a simple (very) circuit with just a resistor (1k) and cap (10n) and voltage source in series.
Using the .net command , I'm getting what I'd expect as the input impedance.
At low frequencies impedance is high (100Kohms +) with -90deg , give or take , phase shift.
As the frequency increases the impedance closes on 1K and the phase shift tends towards 0.

If , however I calculate the input impedance using a formula V(n001) / I(R1) I get a different result.
The resistive portion is correct and starts high and goes towards 1K as frequency increases.
The phase shift however starts at 90 deg and increases to 180 degrees as the frequency goes up???
What am I doing wrong here?
Here is a LTSpice file.

Version 4
SHEET 1 880 680
WIRE -144 112 -272 112
WIRE 16 112 -80 112
WIRE 16 192 16 112
WIRE -272 288 -272 192
WIRE -160 288 -272 288
WIRE 16 288 16 272
WIRE 16 288 -160 288
WIRE -160 304 -160 288
FLAG -160 304 0
SYMBOL res 32 288 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL voltage -272 96 R0
WINDOW 123 24 124 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value ""
SYMATTR Value2 AC 10
SYMBOL cap -80 96 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 10n
TEXT -440 440 Left 2 !.ac dec 1000 10 100k
TEXT -440 376 Left 2 !.net V1 I(R1)

cheers
Ned

- - - Updated - - -

Ok , figured it out.
It's to do with the indicated current direction in R1. LTSpice shows the current flowing into V1.
If I modify the formula to V(n001) / -I(R1) it all sorts itself out. Or subtract 180 degrees.
I'm not sure why LTSpice shows current this way , but Mike Engelhardt at Linear is a lot cleverer
than I am so I'm sure there is a good reason :0)
Cheers
Neddie