## S3 method for class 's_curves':
plot(x, xlim = c(range(mapply(function(i) range(x[[i]][, 1]), seq(x)))),
ylim = c(range(mapply(function(i) range(x[[i]][, 2]),
seq(x)))) * 10000, expoints = NULL,
xlab = "Maturity (years)", ylab = "Spread (basis points)",
lwd = 2, lty = 1, main = "Spread curves", ...)