added files

1.plot

+set parametric
+f(t) = cos(t)
+g(t) = sin(t)
+plot [0:2*pi] f(t),g(t) lt rgb "#008000" lw 2
\ No newline at end of file

2.plot

+set xrange [-10:10]
+set yrange [-10:10]
+poly(x) = 0
+poly1(x) = x**2 - 2 * x
+poly2(x) = x**2 - 4 * x
+poly3(x) = x**2 - 6 * x
+plot [-10:10] poly(x) lt rgb "#A9A9A9" lw 2 dt (2,5,2,5), poly1(x) lt rgb "#8B008B" lw 2, poly2(x) lt rgb "#2E8B57" lw 2, poly3(x) lt rgb "#1E90FF" lw 2
\ No newline at end of file

5.plot

+set grid
+set xtics 1
+set xlabel "Roll No. -->"
+set xrange [0:21]
+set yrange [3:11]
+set style textbox opaque
+set ylabel "Gradepoint -->"
+f(x) = x<=39 ? 4 : \
+       x>=40 && x<=44 ? 5 : \
+       x>=45 && x<=49 ? 6 : \
+       x>=50 && x<=54 ? 7 : \
+       x>=55 && x<=59 ? 8 : \
+       x>=60 && x<=69 ? 9 : 10
+set datafile separator ","
+plot 'test.csv' using 1:(f($2)) title "Grade Chart" with lines lw 3, \
+     ''         using 1:(f($2)):(sprintf("%d", $2)) with labels center boxed notitle
\ No newline at end of file

test.csv

+Roll,Marks
+1,56
+2,34
+3,37
+4,49
+5,52
+6,27
+7,48
+8,51
+9,54
+10,50
+11,65
+12,43
+13,57
+14,76
+15,44
+16,61
+17,27
+18,58
+19,55
+20,53