You might try posting on r-sig-geo if you don't get a satisfactory
response here. I assume there's a lot of expertise there on handling
raster-type data.
Cheers,
Bert
On Mon, Sep 23, 2024 at 11:31 PM javad bayat <j.bayat...@gmail.com> wrote:
>
> Dear R users;
> I have downloaded a grib file format (Met.grib) and I want to export its
> data to excel file. Also I want to do some mathematic on some columns. But
> I got error. I would be more than happy if anyone can help me to do this. I
> have provided the codes and the Met.grib file in this email.
> Sincerely yours
>
> # Load the necessary libraries
> > library(raster) # For reading GRIB files
> > library(dplyr) # For data manipulation
> > library(lubridate) # For date manipulation
> > library(openxlsx) # For writing Excel files
>
> # Specify the file paths
> > grib_file_path <- "C:/Users/Omrab_Lab/Downloads/Met.grib"
> > excel_file_path <- "C:/Users/Omrab_Lab/Downloads/Met_updated.xlsx"
>
> # Open the GRIB file
> > raster_data <- stack(grib_file_path)
>
> # Check the names of the layers to identify which ones to extract
> > layer_names <- names(raster_data)
> > print(layer_names) # Prints
>
>
> > # Extract layers based on layer names - adjust as necessary
> > t2m <- raster_data[[grep("t2m", layer_names)]]
> > d2m <- raster_data[[grep("d2m", layer_names)]]
> > tcc <- raster_data[[grep("tcc", layer_names)]]
> > valid_time <- raster_data[[grep("valid_time", layer_names)]]
> > t2m
> class : RasterStack
> nlayers : 0
>
> > # Check if the raster layers are loaded correctly
> > if (is.null(t2m) || is.null(d2m) || is.null(tcc) || is.null(valid_time))
> {
> + stop("One or more raster layers could not be loaded. Please check the
> layer names.")
> + }
>
> > # Convert raster values to vectors
> > t2m_values <- values(t2m)
> Error in dimnames(x) <- dn :
> length of 'dimnames' [2] not equal to array extent
> > d2m_values <- values(d2m)
> Error in dimnames(x) <- dn :
> length of 'dimnames' [2] not equal to array extent
> > tcc_values <- values(tcc)
> Error in dimnames(x) <- dn :
> length of 'dimnames' [2] not equal to array extent
> > valid_time_values <- values(valid_time)
> Error in dimnames(x) <- dn :
> length of 'dimnames' [2] not equal to array extent
>
> # Check for NA values and dimensions
> if (any(is.na(t2m_values)) || any(is.na(d2m_values)) || any(is.na(tcc_values))
> || any(is.na(valid_time_values))) {
> warning("One or more layers contain NA values. These will be removed.")
> }
>
> # Create the data frame, ensuring no NA values are included
> df <- data.frame(
> t2m = t2m_values,
> d2m = d2m_values,
> tcc = tcc_values,
> valid_time = valid_time_values,
> stringsAsFactors = FALSE
> )
>
> # Remove rows with NA values
> df <- na.omit(df)
>
> # Convert temperatures from Kelvin to Celsius
> df$t2m <- df$t2m - 273.15
> df$d2m <- df$d2m - 273.15
>
> # Calculate relative humidity
> calculate_relative_humidity <- function(t2m, d2m) {
> es <- 6.112 * exp((17.67 * t2m) / (t2m + 243.5))
> e <- 6.112 * exp((17.67 * d2m) / (d2m + 243.5))
> rh <- (e / es) * 100
> return(rh)
> }
> df$RH <- calculate_relative_humidity(df$t2m, df$d2m)
>
> # Convert valid_time from numeric to POSIXct assuming it's in seconds since
> the epoch
> df$valid_time <- as.POSIXct(df$valid_time, origin = "1970-01-01")
>
> # Extract year, month, day, and hour from valid_time
> df$Year <- year(df$valid_time)
> df$Month <- month(df$valid_time)
> df$Day <- day(df$valid_time)
> df$Hour <- hour(df$valid_time)
>
> # Select only the desired columns
> df_selected <- df %>% select(Year, Month, Day, Hour, tcc, t2m, RH)
>
> # Save the updated DataFrame to an Excel file
> write.xlsx(df_selected, excel_file_path, row.names = FALSE)
>
>
>
>
>
>
> --
> Best Regards
> Javad Bayat
> M.Sc. Environment Engineering
> Alternative Mail: bayat...@yahoo.com
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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______________________________________________
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PLEASE do read the posting guide https://www.R-project.org/posting-guide.html
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