R seq() 函数 - 生成序列
R 语言实例R seq() 函数用于生成有规律的数值序列。
seq() 比冒号运算符 : 更灵活，可以指定步长或序列长度。
seq() 函数语法格式如下：
seq(from = 1, to = 1, by = ((to - from)/(length.out - 1)), length.out = NULL)
参数说明：
from 起始值。
to 结束值。
by 步长（增量）。
length.out 想要生成的序列长度。
实例
# 基本用法：指定步长
print("步长为 2:")
print(seq(from = 1, to = 10, by = 2))
print("步长为 0.5:")
print(seq(from = 0, to = 3, by = 0.5))
# 指定长度
print("等分为 5 个点:")
print(seq(from = 1, to = 10, length.out = 5))
# 逆序序列
print("逆序:")
print(seq(from = 10, to = 1, by = -2))
print("步长为 2:")
print(seq(from = 1, to = 10, by = 2))
print("步长为 0.5:")
print(seq(from = 0, to = 3, by = 0.5))
# 指定长度
print("等分为 5 个点:")
print(seq(from = 1, to = 10, length.out = 5))
# 逆序序列
print("逆序:")
print(seq(from = 10, to = 1, by = -2))
执行以上代码输出结果为：
[1] "步长为 2:" [1] 1 3 5 7 9 [1] "步长为 0.5:" [1] 0.0 0.5 1.0 1.5 2.0 2.5 3.0 [1] "等分为 5 个点:" [1] 1.00 3.25 5.50 7.75 10.00 [1] "逆序:" [1] 10 8 6 4 2
seq() 在绘图和数据生成中非常常用，例如创建 x 轴坐标点：
实例
# 生成绘图用 x 坐标
x <- seq(-pi, pi, length.out = 100)
# 计算对应的 y = sin(x)
y <- sin(x)
# 打印前几个点
print("前 5 个坐标点:")
for (i in 1:5) {
cat(sprintf("(%.2f, %.2f)\n", x[i], y[i]))
}
x <- seq(-pi, pi, length.out = 100)
# 计算对应的 y = sin(x)
y <- sin(x)
# 打印前几个点
print("前 5 个坐标点:")
for (i in 1:5) {
cat(sprintf("(%.2f, %.2f)\n", x[i], y[i]))
}
执行以上代码输出结果为：
[1] "前 5 个坐标点:" (-3.14, -0.00) (-3.08, -0.06) (-3.01, -0.13) (-2.95, -0.19) (-2.89, -0.25)