Plot power consumption as a function of temperature

gistfile1.gp

#!/usr/bin/env gnuplot

# sqlite3
# select cast(temp as integer), round(avg(1000*usage), 2) from power group by 1;

set terminal png
set output "data.png"
set datafile separator ","

set title "Power consumption as a function of temperature"
set ylabel "Watts"
set xlabel "Outside temperature (Celsius)"

f(x) = a*x + b
fit [-20:10] f(x) 'data.txt' using 1:2 via a,b

plot "data.txt" title "Power usage", \
     f(x) title "linear fit -20..10C"