使用ncdf4包从.csv到.nc文件(ncvar_put中的错误)

Question

我正在尝试从.csv文件写入.nc文件。

这是我的.csv表(df)的一部分

 long        lat     elev
1  -47.99206  -7.501234 242.0362
2  -47.99206  -7.751234 200.7271
3  -47.99206  -8.001234 165.6918
4  -47.99206  -8.251234 271.2571
5  -47.99206  -8.501234 235.2896
6  -47.99206  -8.751234 271.5381
7  -47.99206  -9.001234 290.0054
8  -47.99206  -9.251234 218.8803
9  -47.99206  -9.501234 261.7539
10 -47.99206  -9.751234 318.0000
11 -47.99206 -10.001234 314.3667
12 -47.99206 -10.251234 386.0861
13 -47.99206 -10.501234 446.0594
14 -47.99206 -10.751234 733.0910
15 -47.99206 -11.001234 316.2924
16 -47.99206 -11.251234 264.8820
17 -47.74206  -7.501234 262.5883
18 -47.74206  -7.751234 197.8402
19 -47.74206  -8.001234 246.0610
20 -47.74206  -8.251234 264.7328

...

如你所见，我有两个维度和一个变量。

这是我使用的代码：

xvals <- unique(df$long)
xvals <- xvals[order(xvals)]
yvals = unique(df$lat)
yvals <- yvals[order(yvals)] 

lon <- ncdim_def("longitude", "degrees", xvals)
lat <- ncdim_def("latitude", "degrees", yvals)

var_elev <- ncvar_def("elev", "m above sea", 
                      list(lon, lat), NA) 

ncnew <- nc_create('elev.nc', var_elev)

ncvar_put(ncnew, "elev", df$elev, count = c(35, 51))

当我运行最后一行时，我收到以下错误消息：

Error in ncvar_put(ncnew, "elev", df$elev, count = c(35, 51)) : 
  ncvar_put: error: you asked to write 1785 values, but the passed data array only has 959 entries!

有关我的尺寸的更多信息：

yvals唯一值：

yvals
 [1] -15.001234 -14.751234 -14.501234 -14.251234 -14.001234
 [6] -13.751234 -13.501234 -13.251234 -13.001234 -12.751234
[11] -12.501234 -12.251234 -12.001234 -11.751234 -11.501234
[16] -11.251234 -11.001234 -10.751234 -10.501234 -10.251234
[21] -10.001234  -9.751234  -9.501234  -9.251234  -9.001234
[26]  -8.751234  -8.501234  -8.251234  -8.001234  -7.751234
[31]  -7.501234  -7.251234  -7.001234  -6.751234  -6.501234
[36]  -6.251234  -6.001234  -5.751234  -5.501234  -5.251234
[41]  -5.001234  -4.751234  -4.501234  -4.251234  -4.001234
[46]  -3.751234  -3.501234  -3.251234  -3.001234  -2.751234
[51]  -2.501234

xvals唯一值：

xvals
 [1] -50.49206 -50.24206 -49.99206 -49.74206 -49.49206 -49.24206
 [7] -48.99206 -48.74206 -48.49206 -48.24206 -47.99206 -47.74206
[13] -47.49206 -47.24206 -46.99206 -46.74206 -46.49206 -46.24206
[19] -45.99206 -45.74206 -45.49206 -45.24206 -44.99206 -44.74206
[25] -44.49206 -44.24206 -43.99206 -43.74206 -43.49206 -43.24206
[31] -42.99206 -42.74206 -42.49206 -42.24206 -41.99206

elev列有959个唯一值。

此外，我不确定重新排序维度是否会给我提供long、lat和elev之间的正确对应关系。无论如何，我完全不知道如何解决这个问题。

谢谢大家！

Answer 1

您正在尝试使用ncdim_def定义一个2D数组，但只将一个1D向量传递给dataset。您需要将数据帧的观测值转换为2D数组。这可以使用tidyr来完成：

library(tidyr)
# Example df with same names
df <- data.frame(long = rep(1:10,2), lat = 1:40, elev = 1:40)
# Creates a 2D array
df_new <- tidyr::pivot_wider(df, names_from = long, values_from = elev)
df_new <- df_new[,-1]

现在试一下

ncvar_put(ncnew, elev, as.matrix(df_new))