set terminal pngcairo size 500, 500 enhanced font 'Verdana, 10'

f(x) = a + b * x

fit f(x) 'data2' u 3:1 via a, b

set ylabel 'T, deg'
set xlabel 'p, кгс'
plot 'data2' using 3:1:4:2 w xyerrorbars title 'pressure-plot', f(x) title 'fitting line'

pause -1