我们在做各种模型训练时，往往会先将数据处理成矩阵，然后交给建模的人去训练。这时通常数据清洗者提交的是保存了矩阵的文件，一般为TXT或csv，接下来主要讲解我在实现这个过程中遇到的一些问题。
import numpy numpy.savetxt('new.csv', my_matrix, delimiter=',')
看上面这段d代码，通常我们会直接使用上面这两句代码来进行保存。但通常会遇到下面两类错误：
1. 类型匹配错误
如上面截图。原因是：loadtxt()这个函数本身在默认情况下认为数据元素都是数值型的，所以用%.18e的格式去读取。所以当遇到str或其他非数值型时就会出错。这里是的指定数据类型解决的。正确代码如下：
import numpy numpy.savetxt('new.csv', my_matrix, fmt='%s', delimiter=',')
2. 存入csv文件时，部分数据丢失
原因，csv默认是用逗号分隔的，所以如果你的数据中含有逗号，就会被它识别，因此在存入之前，应先将逗号进行提换或者加转义字符。
这里补充一下saveTXT的原型：
numpy.savetxt
- numpy.savetxt(fname, X, fmt='%.18e', delimiter=' ', newline='\n', header='', footer='', comments='# ')[source]
-
Save an array to a text file.
Parameters: fname : filename or file handle
If the filename ends in .gz, the file is automatically saved in compressed gzip format. loadtxt understands gzipped files transparently.
X : array_like
Data to be saved to a text file.
fmt : str or sequence of strs, optional
A single format (%10.5f), a sequence of formats, or a multi-format string, e.g. ‘Iteration %d – %10.5f’, in which case delimiter is ignored. For complex X, the legal options for fmt are:
- a single specifier, fmt=’%.4e’, resulting in numbers formatted
-
like ‘ (%s+%sj)’ % (fmt, fmt)
- a full string specifying every real and imaginary part, e.g.
-
‘ %.4e %+.4ej %.4e %+.4ej %.4e %+.4ej’ for 3 columns
- a list of specifiers, one per column - in this case, the real
-
and imaginary part must have separate specifiers, e.g. [‘%.3e + %.3ej’, ‘(%.15e%+.15ej)’] for 2 columns
delimiter : str, optional
String or character separating columns.
newline : str, optional
String or character separating lines.
New in version 1.5.0.
header : str, optional
String that will be written at the beginning of the file.
New in version 1.7.0.
footer : str, optional
String that will be written at the end of the file.
New in version 1.7.0.
comments : str, optional
String that will be prepended to the header and footer strings, to mark them as comments. Default: ‘# ‘, as expected by e.g. numpy.loadtxt.
New in version 1.7.0.
Notes
Further explanation of the fmt parameter (%[flag]width[.precision]specifier):
- flags:
-
- : left justify
+ : Forces to precede result with + or -.
0 : Left pad the number with zeros instead of space (see width).
- width:
- Minimum number of characters to be printed. The value is not truncated if it has more characters.
- precision:
-
- For integer specifiers (eg. d,i,o,x), the minimum number of digits.
- For e, E and f specifiers, the number of digits to print after the decimal point.
- For g and G, the maximum number of significant digits.
- For s, the maximum number of characters.
- specifiers:
-
c : character
d or i : signed decimal integer
e or E : scientific notation with e or E.
f : decimal floating point
g,G : use the shorter of e,E or f
o : signed octal
s : string of characters
u : unsigned decimal integer
x,X : unsigned hexadecimal integer
This explanation of fmt is not complete, for an exhaustive specification see [R280].
