plots

png(file="001_sample.png",width=500, height=500)
par(mfrow=c(1,1), family="HiraKakuProN-W3")
plot(10,10,type="n", ylim=c(0,12), xlim=c(-100,100), yaxt="n", ylab="")

abline(h=12)
abline(h=9)
for(i in seq(-80,98)){
    lines(c(i,i+2), c(12,9), lwd=0.3)	
}


abline(h=8, col="blue")
abline(h=5, col="blue")
for(i in seq(-30,10,0.1)){
    lines(c(i,i^2), c(8,5), col="blue", lwd=0.3)	
}


abline(h=4, col="red")
abline(h=1, col="red")
for(i in seq(-10,10,0.1)){
    lines(c(i,i^3), c(4,1), col="red", lwd=0.3)	
}

abline(v=0, col="red", lty="dashed")

legend("topleft", legend=c("1次関数","2次関数","3次関数"), col=c("black","blue","red"), lty=c(1,1,1), bg="white")

dev.off()


png(file="002_sample.png",width=500, height=500)
par(mfrow=c(1,1), family="HiraKakuProN-W3")
plot(1,1,type="n", ylim=c(-100,100),xlim=c(-20,20))
abline(a=1, b=2, lwd=3)
x <- seq(-20,20, 0.1)
lines(x, x^2, lwd=3, col="blue")
lines(x, x^3, lwd=3, col="red")

legend("topleft", legend=c("1次関数","2次関数","3次関数"), col=c("black","blue","red"), lty=c(1,1,1), bg="white")

dev.off()