STATA高级：使用ftp数据及字符串序列问题

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问题1：

    stata可以引用http协议下得数据，不知道对于ftp目录中的数据什么命令可以实现访问

问题2：

    循环中依次使用某数据序列中的数据时，可以先将数据存在一个矩阵中，但是矩阵不能存储字符串，同样的调用字符串的功能有没有办法实现呢。

    比如在一个地方写入31个省、市、自治区的名字，然后循环31次依次调用这31个字符串（它们的长度好像没什么规律）。

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关键词：STATA高级 Stata tata 字符串 FTP 数据 序列 Stata FTP 字符

Q1：

   这个问题此前统计局有位朋友也探讨过，不过好像没有什么好的办法。建议到 stata list（http://www.stata.com/statalist）中发个Email，那里集中了全世界的stata高人，应该会有解答。

Q2：

   若使用stata原来的矩阵功能（matrix命令），确实无法处理字符串。但自stata9以来，有了mata语句，可以在矩阵中处理字符串了。

   就你的问题而言，或许可以考虑先把31个省份的名称转换成代码（encode命令），然后再对这些代码（数字类型）进行循环操作即可。

Bookbug:

   我到stata官方网站查询了这个问题（你可以在stata主页右上角搜索区输入 “ftp data”关键字进行搜索），似乎没有很好的解决办法。下面是相关信息：

Re: st: reading data from ftp site?

---

From	ariley@stata.com (Alan Riley)
To	statalist@hsphsun2.harvard.edu
Subject	Re: st: reading data from ftp site?
Date	Thu, 25 Jan 2007 12:08:46 -0600

---

Paulo Guimaraes (guimaraes@moore.sc.edu) would like to download data from an FTP site directly into Stata: > I would like to know if it is possible to read data directly from an ftp > site. > My interest in this is because I need to access some flat files at the BLS > web site. > Right now what I do is to open the file in my web browser and then save it > and insheet it into Stata. > For example, to read the employment time series for the state of Alabama I > need to open the file in my web browser > with the command: > ftp://ftp.bls.gov/pub/time.series/sm/sm.data.1.Alabama > and then save it and read it into Stata. > Is it possible to read the data directly from within Stata? Anders Alexandersson (andersalex@gmail.com) suggested that it may be possible to do this directly in Stata: > I don't think you need to resort to mapping. The user manual [U] 28.2 > suggests the Stata -copy- command for sharing other files than Stata > datasets (for which -use- is a direct solution). Although the URL > examples are for http, and I have not tried ftp, ftp is another type > of URL so it should work. Stata currently supports only the 'http' protocol for accessing files on the internet. URLs beginning with 'ftp://' and protocols other than 'http://' are not supported. Paulo should be able to do as Austin Nichols (austinnichols@gmail.com) suggested: > There are probably several platform-specific approaches. One is to > "map an ftp server as a drive" or whatever the equivalent operation is > in your OS. In various flavors of Windows, there are several apps > that can map a drive letter to an ftp server, at which point the > standard infiling commands should work fine. Depending on the operating system Paulo is using, command-line utilities such as 'curl' or 'wget' may also be available which support downloading data using a variety of protocols, including ftp. Paulo could use Stata's -shell- command to access such a command to download a file via ftp. Alan (ariley@stata.com) 

多谢连博士回复

又找到一个方法：http://www.stata.com/statalist/archive/2007-05/msg00494.html

st: how to make a string matrix

---

From	Kit Baum <baum@bc.edu>
To	statalist@hsphsun2.harvard.edu
Subject	st: how to make a string matrix
Date	Tue, 15 May 2007 11:55:07 -0400

---

sacrificial rutabaga

Along with Bill Gould's solution for using Mata to hold a "string matrix", also note that such a creature can be handled by using a set of locals:

local row1 a b c d e
local row2 f g h i j k l
local row3 m n o p
local row4 q r s t u v
local row5 w x y z

local row 3
local col 2
local element : word `col' of `row`row''
di "S[`row',`col'] is `element'"

Note that unlike standard matrices, such a 'matrix' can have a different number of elements per row.

Some may note the resemblance between this solution and an array of pointers to arrays.


Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/

Baum的确是个高手，呵呵。