No data available in table

这个错误信息通常表示你读取的文件中没有数据。这可能是因为你指定的文件路径不正确，或者文件中确实没有数据。

首先，请确保你指定的文件路径是正确的。你可以使用 `getwd()` 命令查看当前的工作目录，并使用 `setwd()` 命令来设置正确的工作目录。你还可以使用全路径来指定文件路径，例如：

data <- read.table("/Users/username/Documents/data.txt", header=TRUE)

如果你确定路径正确但仍然无法读取数据，则可能是因为文件确实为空或者文件格式有误。你可以使用 `file.info()` 命令检查文件的大小和修改时间，以确保文件不是空文件。另外，你可以尝试使用 `read.csv()` 或者 `read.delim()` 命令来读取文件，以确保文件格式正确。

如果你还是无法读取数据，请提供更多详细信息，例如数据文件的类型和结构，以便我更好地帮助你解决问题。

相关问题

r语言读取excel文件里面代码为1的股票数据显示No data available in table

如果你使用以下代码：

data <- read_excel("your_file_path.xlsx")
stock_data <- data[data$code == 1, ]

但是得到了"No data available in table"的错误信息，那么可能是因为Excel文件中没有代码为1的股票数据。

你可以使用以下代码来检查Excel文件中是否有代码为1的股票数据：

data <- read_excel("your_file_path.xlsx")
unique(data$code) # 显示Excel文件中所有不同的代码

如果输出结果中没有1这个代码，那么就说明Excel文件中没有代码为1的股票数据。

Write a program to 1.Setup a simulating backing store in memory. Read the data from pdata.bin to this backing store. 2.Initialize a page table for process p, set the frame number to be -1 for each page, indicating that the page is not loaded into memory yet. 3.Read logical addresses one by one from la.txt. 4.For each logical address, a)if its page has been loaded into physical memory, simply find the frame number in the page table, then generate physical address, find and print out the physical address and data inside this address. b)if the page is used for the first time, i.e., in page table, its frame number is -1，then the page that contains this address should be loaded into a free frame in physical memory (RAM). Then update the page table by adding the frame number to the right index in the page table. Then repeat 4a). Assumption: 1.Assume the file la.txt includes the sequence of generated addresses from CPU. 2.Use a part of memory as backing store that store data for a process. 3.The backing store size is 128 bytes 4.The size of process p is 128 bytes. 5.The contents of p is included in a file pdata.bin which is a binary file. 6.Use a part of memory as RAM. The size of physical memory is 256 bytes, from 0 to 255. All the physical memory is available, allocating starting from beginning in sequence. That is, allocate frame 0 first, then frame 1, then frame 2…. 7.The size of a frame is 32 bytes, i.e., 5 bits for the offset in a frame, total number of frames is 8. At beginning, no page table is available for process p.

Here is a sample program that implements the steps you described:

BACKING_STORE_SIZE = 128
PHYSICAL_MEMORY_SIZE = 256
PAGE_SIZE = 32
NUM_FRAMES = PHYSICAL_MEMORY_SIZE // PAGE_SIZE

# Initialize backing store
backing_store = bytearray(BACKING_STORE_SIZE)
with open("pdata.bin", "rb") as f:
    pdata = f.read()
    backing_store[:len(pdata)] = pdata

# Initialize page table
page_table = [-1] * (BACKING_STORE_SIZE // PAGE_SIZE)

# Initialize physical memory
physical_memory = [bytearray(PAGE_SIZE) for _ in range(NUM_FRAMES)]

# Read logical addresses from la.txt
with open("la.txt", "r") as f:
    for line in f:
        logical_address = int(line.strip())
        page_number = logical_address // PAGE_SIZE
        offset = logical_address % PAGE_SIZE

        # Check if page is already in physical memory
        frame_number = page_table[page_number]
        if frame_number != -1:
            physical_address = frame_number * PAGE_SIZE + offset
            data = physical_memory[frame_number][offset]
            print("Physical address:", physical_address, "Data:", data)

        # If page is not in physical memory, load it
        else:
            # Find a free frame in physical memory
            frame_number = None
            for i in range(NUM_FRAMES):
                if page_table.count(i) == 0:
                    frame_number = i
                    break

            if frame_number is None:
                print("Error: no free frame available in physical memory")
                break

            # Load page from backing store to physical memory
            page_start = page_number * PAGE_SIZE
            page_data = backing_store[page_start:page_start + PAGE_SIZE]
            physical_memory[frame_number][:] = page_data

            # Update page table
            page_table[page_number] = frame_number

            # Print physical address and data
            physical_address = frame_number * PAGE_SIZE + offset
            data = physical_memory[frame_number][offset]
            print("Physical address:", physical_address, "Data:", data)

Here is an overview of how the program works:

1. The program initializes the backing store by reading the contents of `pdata.bin` into a byte array. It also initializes the page table with -1 values, indicating that no pages are loaded into physical memory yet.

2. The program creates a byte array for each frame in physical memory, and initializes them all to 0.

3. The program reads logical addresses from `la.txt` one by one.

4. For each logical address, the program computes the page number and offset.

5. If the page is already loaded into physical memory (i.e., its frame number is not -1), the program computes the physical address and reads the data from the corresponding byte array in physical memory.

6. If the page is not yet loaded into physical memory, the program searches for a free frame, loads the page from the backing store to the frame, updates the page table with the frame number, and then reads the data from the corresponding byte array in physical memory.

7. The program prints the physical address and data for each logical address.

Note that this program assumes that there is always at least one free frame in physical memory. If there are no free frames, the program will print an error message and stop.