Question

我的data.frame（movement.data）看起来像这样：

head(movement.data)

  Longitude  Latitude  Sample     X        Y
1  -1.581638 53.81659 1099.99 95.41699 65.88299
2  -1.581642 53.81659 1100.09 95.17410 65.89411
3  -1.581646 53.81659 1100.19 94.93121 65.80516
4  -1.581650 53.81659 1100.30 94.65550 65.74956
5  -1.581650 53.81659 1100.30 94.65550 65.74956
6  -1.581654 53.81659 1100.49 94.41261 65.60501
7  -1.581657 53.81659 1100.59 94.20254 65.59389
8  -1.581660 53.81659 1100.69 93.97934 65.57165
9  -1.581662 53.81659 1100.80 93.88088 65.54941
10 -1.581662 53.81659 1100.80 93.88088 65.54941
11 -1.581661 53.81659 1100.90 93.90714 65.42709
12 -1.581661 53.81659 1101.00 93.89401 65.50493
13 -1.581660 53.81659 1101.19 93.96621 65.69396
14 -1.581658 53.81659 1101.29 94.12376 65.76068



> structure(list(Longitude = c(-1.5816382, -1.5816419, -1.5816456, 
-1.5816498, -1.5816498, -1.5816535, -1.5816567, -1.5816601, -1.5816616, 
-1.5816616, -1.5816612, -1.5816614, -1.5816603, -1.5816579, -1.5816551, 
-1.581652), Latitude = c(53.8165922, 53.8165923, 53.8165915, 
53.816591, 53.816591, 53.8165897, 53.8165896, 53.8165894, 53.8165892, 
53.8165892, 53.8165881, 53.8165888, 53.8165905, 53.8165911, 53.8165925, 
53.8165926), Sample = c(1099.99, 1100.09, 1100.19, 1100.3, 1100.3, 
1100.49, 1100.59, 1100.69, 1100.8, 1100.8, 1100.9, 1101, 1101.19, 
1101.29, 1101.39, 1101.5), X = c(95.4169935430477, 95.1741017603222, 
94.9312120174133, 94.6554984032894, 94.6554984032894, 94.4126097693692, 
94.2025416091894, 93.9793443981241, 93.8808752899916, 93.8808752899916, 
93.9071363032427, 93.8940054603786, 93.9662126575805, 94.1237625957496, 
94.3075692760132, 94.5110727848407), Y = c(65.8829940372709, 
65.8941135300653, 65.8051575885002, 65.7495601253183, 65.7495601253183, 
65.6050067205713, 65.5938872277769, 65.5716482421881, 65.5494092573894, 
65.5494092573894, 65.4270948374411, 65.5049312862118, 65.6939626613463, 
65.7606796173226, 65.9163525148641, 65.9274720076584)), row.names = 11000:11015, class = "data.frame")

我想计算X和Y坐标之间的角位移。我编写了一个for循环来遍历data.frame（请参见下面的代码）。

Angular.Displacement <- vector("numeric", length(movement.data$X))
for (dp in movement.data) {
  i <- 2
  while(i <= length(movement.data$X)) {
      a <- c((movement.data$X[i] - movement.data$X[i - 1]), (movement.data$Y[i] - movement.data$Y[i - 1]))
      b <- c((movement.data$X[i + 1] - movement.data$X[i]), (movement.data$Y[i + 1] - movement.data$Y[i]))
      dot.prod <- a %*% b
      norm.a <- norm(a, type = "2")
      norm.b <- norm(b, type = "2")
      Angular.Displacement[i] = acos((dot.prod) / (norm.a * norm.b)) * (180 / pi)
    i <- i+1
  }
}

虽然此代码有效，但它笨拙且效率不高。我将循环转换为一个函数（compute_angular_displacement-参见下文），以便可以使用dplyr库中的mutate将其应用于data.frame。

compute_angular_displacement <- function(df) {
    # Calculation coefficients
    a <- c((df$X - lag(df$X)), (df$Y - lag(df$Y)))
    b <- c((lead(df$X) - df$X), (lead(df$Y) - df$Y))
    dot.prod <- a %*% b
    norm_a <- norm(a, type = "2")
    norm_b <- norm(b, type = "2")
    # Calculation for angular displacement
    Angular_Displacement = acos((dot.prod)/(norm_a * norm_b)) * (180/pi)
}

但是，当我应用该函数（请参见下面的代码）时，会收到此错误代码（下面是mutate的代码示例）：

movement.data <- mutate(movement.data, Angular_Displacement = compute_angular_displacement(movement.data))

svd（x，nu = 0L，nv = 0L）中的错误：'x'中的值无穷或缺失

我在函数外部手动检查了计算结果。当我将方法和计算应用于从shell中的motion.data选择的数据点时，它们返回了正确的答案。

进一步的研究发现，错误是由使用“ lag”和“ lead”函数引起的，当调用它们时，它们会在c（）中产生NA值，而当“ norm.a < -运行norm（a，type =“ 2”）“。

有人知道如何解决此问题吗？ -一个可能的快速解决方案是我的while循环和函数之间的组合，但是我不确定如何成功实现这一点。在这方面的任何帮助将不胜感激。

将功能应用于数据框时的错误消息

0 个答案: