How do I remove leading characters from a string?

2019 9 18
2 个回答
回答已采纳
更新时间：2019 9 19
12 次查看（30 天）

0 个投票

I read one ascii file. and created this dummy mat file (attached ).
To make simple matrix out of it i need to split the string
i used this code (below) but it coudnt split the first string which is a date and time with some leading number since there is no space in between. There is this number before the date and time, i want remove those numbers so can use datenum on that string !
for i = 1:len_data
segments = regexp(dummy{1,1}{i,1},' ', 'split');
end

请先登录，再回答此问题。

 采纳的回答

Walter Roberson
Walter Roberson 2019-9-18

1 个投票

segments = regexp(dummy{1,1}{i,1}, '\t', 'split');
Perhaps you could have used readtable() on the ascii file: it would likely have detected the tab delimiter.

3 个评论
显示 1更早的评论 隐藏 1更早的评论

pruth
pruth 2019-9-18
Hi walter, thanks for the reply !
your code works fine ! but here even date and time also splits. can you tell me how can just merge 2nd column(date) and 3rd column (time) to use datenum on it !
Walter Roberson
Walter Roberson 2019-9-18
strjoin(segments(2:3), ' ')
Note that we no longer recommend using datenum: we recommend using datetime()

请先登录，再进行评论。

更多回答（1 个）

Ankit
Ankit 2019-9-18

1 个投票

Hello Pruth,
One possibility is to use extractBetween command.
newStr = extractBetween(str,startPos,endPos)
a = extractBetween(dummy{1, 1}, 10,20)
where 10 is the start position and 20 is the end position.
Based on your requirement you can also try extractAfter, extractBefore
Cheers
Ankit

3 个评论
显示 1更早的评论 隐藏 1更早的评论

pruth
pruth 2019-9-18
hi, ankit thanks for the reply !
i used 'extractafter' as you suggested ! it does what I was expecting but i am not able to figure out how convert this cell into normal matrix with 1st coulmn having date and time in matlab format. i want to use datenum here !
i want to create simple matrix.
1st coulmn should be date and time(in matlab format) and next coumns should be data !
I appreciate your help !
Ankit
Ankit 2019-9-18
hello pruth,
cell data can be converted to double using str2double. But you can't use it to convert date, it will return a NaN value.
here you can read: Convert Between Datetime Arrays, Numbers, and Text.
thanks
Ankit
Walter Roberson
Walter Roberson 2019-9-19
However, datetime() is happy to process cell array of character vectors ;-)
Also, in newer releases, duration() is happy to process cell array of character vectors. This was not possible in older releases.

请先登录，再进行评论。

类别

在 帮助中心 和 File Exchange 中查找有关 Dates and Time 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by