使用循环和条件获取R中的斜率

Question

我正在处理一个数据框，它包含x和y列，值作为行。我想计算每2行x和y的斜率，然后使用计算出的斜率，记录斜率的“稳定性”是“高”还是“低”。看过代码后，您会更好地理解。这段代码有什么问题？当我输入稳定时，R返回NULL。

slope <- (acc$y[i+1] - acc$y[i]) / (acc$x[i+1] - acc$x[i])
stability <- c()
for (i in 1:nrow(acc)) {
  if (slope[i] > 0 & slope[i] < 0.8) {
    stability[i] <- "low"
  } else if (slope[i] >= 0.8 & slope[i] <= 1) {
    stability[i] <- "high"
  } else if (slope[i] > 1 & slope[i] < 1.2) {
    stability[i] <- "high"
  } else if (slope[i] >= 1.2) {
    stability[i] <- "low"
  } else if (slope[i] >= -1 & slope[i] <= -0.8) {
    stability[i] <- "high"
  } else if (slope[i] >= -0.8 & slope[i] <= 0) {
    stability[i] <- "low"
  } else if (slope[i] < -1 & slope[i] > -1.2) {
    stability[i] <- "high"
  } else 
    stability[i] <- "low"
}

Answer 1

如下所示修改您的代码：

    #slope <- (acc$y[i+1] - acc$y[i]) / (acc$x[i+1] - acc$x[i])
     stability <- as.vector(nrow(acc))       
    n <- nrow(acc)-1
    for (i in 1:n) {
      slope <- (acc$y[i+1] - acc$y[i]) / (acc$x[i+1] - acc$x[i])         

      if (slope > 0 && slope < 0.8) {
        stability[i] <- "low"
      } else if (slope >= 0.8 && slope <= 1) {
        stability[i] <- "high"
      } else if (slope > 1 && slope < 1.2) {
        stability[i] <- "high"
      } else if (slope >= 1.2) {
        stability[i] <- "low"
      } else if (slope >= -1 && slope <= -0.8) {
        stability[i] <- "high"
      } else if (slope >= -0.8 && slope <= 0) {
        stability[i] <- "low"
      } else if (slope < -1 && slope > -1.2) {
        stability[i] <- "high"
      } else
        stability[i] <- "low"
    }

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