textscan: skipping rows with missing data
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I'm using textscan() to open large txt files. Every so often I get a line where the value in the third column is missing, so everything gets shifted and text scan stops reading the data and just returns everything up until this point. The data kind of looks like this, although really it's 5 string columns followed by 30 double columns. It doesn't seem to want to preserve my formatting which would make it easier to see but I think this is still helpful
string string double double double
string double double double
string string double double double
string string double double double
string string double double double
Does anyone know a way to deal with that other than going in and manually deleting those incomplete lines from the individual text files?
4 个评论
per isakson
2014-12-2
The columns are they separated by tab or space?
Kendra Wright
2014-12-2
Kendra Wright
2014-12-2
Thorsten
2014-12-3
It would be helpful if you post your file, or at least some of the lines with the different number of columns.
回答（2 个）
per isakson
2014-12-2
编辑：per isakson
2014-12-3
"columns are separated by tabs"
textscan should take care of missing data automagically!  Replace 'Delimiter', ',' by 'Delimiter', ','\t' in these examples
>> cac = textscan( 'abc,,1,2,3', '%s%s%f%f%f', 'Delimiter', ',' )
cac =
{1x1 cell} {1x1 cell} [1] [2] [3]
>> cac{2}
ans =
{''}
>>
and
>> cac = textscan( 'abc,def,1,,3', '%s%s%f%f%f', 'Delimiter', ',' )
cac =
{1x1 cell} {1x1 cell} [1] [NaN] [3]
 
"Then when there is the bad line it has tab+ a few spaces in place of the missing strings"
>> cac = textscan( 'abc, ,1,2,3', '%s%s%f%f%f', 'Delimiter', ',' )
cac =
{1x1 cell} {1x1 cell} [1] [2] [3]
>> cac{2}
ans =
{''}
and
>> cac = textscan( 'abc,def,1, ,3', '%s%s%f%f%f', 'Delimiter', ',' )
cac =
{1x1 cell} {1x1 cell} [1] [NaN] [3]
 
@Star's proposal: MultipleDelimsAsOne
>> textscan( 'a b c,d e f,1,2,3', '%s%s%s%s%s%s%f%f%f' ...
, 'Delimiter', ', ', 'MultipleDelimsAsOne', true )
ans =
Columns 1 through 6
{1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell}
Columns 7 through 9
[1] [2] [3]
So far so good. However, with "b" missing
textscan( 'a c,d e f,1,2,3', '%s%s%s%s%s%s%f%f%f' ...
, 'Delimiter', ', ', 'MultipleDelimsAsOne', true )
ans =
Columns 1 through 6
{1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell} {1x1 cell}
Columns 7 through 9
[2] [3] [0x1 double]
it returns an erroneous result
6 个评论
Kendra Wright
2014-12-2
Kendra Wright
2014-12-2
per isakson
2014-12-2
编辑：per isakson
2014-12-2
"space space tab space space tab tab tab tab tab (30 times)"   That's weird! Is there a tab in front of the first numeric?
"Can textscan do that?"
I'm not sure. Some spaces are delimiters and other spaces happens to be there because of missing data. The latter should be ignored. It's worth trying to read the file with tab as delimiter and in a second step parse the string columns.
Star Strider
2014-12-2
In the online documentation for textscan there’s an option (under ‘Examples’ > ‘Treat Repeated Delimiters as One’) to use the 'MultipleDelimsAsOne',1 name-value pair.
Seems worth a try, anyway.
Kendra Wright
2014-12-3
per isakson
2014-12-3
编辑：per isakson
2014-12-3
Consider the strings containing space separated letters
'a b c'
' b c'
'a c'
one need additional information to be able to decide whether 'a' or 'b' is missing. That has little with limitations of Matlab to do.
Why don't you attach a small sample file.
Thorsten
2014-12-2
0 个投票
I think that you have to read individual lines with fgets and then deal with the cases of missing values.
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