Problems getting the size of a cell array

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Anshuman Pal
Anshuman Pal 2020 年 4 月 14 日
コメント済み: Anshuman Pal 2020 年 4 月 14 日
Hi,
I know that one can usually get the size of a cell array using size(). However, I am facing this particular case -- where I am trying to read data from a .txt file, and save it to a matrix -- where a particular row of the cell (data.textdata{2}) just refuses to show its actual size on using size(). I need the length to loop over data.textdata{2}.
filename = 'test'
data = importdata([filename '.rpt']) ;
%% data is in data.textdata. In particular, data.textdata{2}, which is a matrix, refuses to show its size.
size(data.textdata{2}) % only gives the size of the first character array
I am attaching the code and the text file. Can someone please help?
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Anshuman Pal
Anshuman Pal 2020 年 4 月 14 日
Sorry, the .rpt above and in the code should be substitued with .txt.

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回答 (1 件)

Walter Roberson
Walter Roberson 2020 年 4 月 14 日
You have
data.textdata{2,1} = [];
That does not delete an existing data.textdata{2,1} : it assigns the empty array inside it.
size(data.textdata{2})
{2} is linear indexing into the 7 x 17478 cell array, and is equivalent to {2,1} when there is more than one row. So size(data.textdata{2}) is the same as size(data.textdata{2,1}) which is the object you just set to [], so the returned size is, quite correctly, 0 x 0.
If you want to know how many entries are in the row, then size(data.textdata,2) --- where 2 refers to the second dimension, not to row number 2.
I would suggest to you that you instead use
data = table2array(readtable([filename '.rpt'], 'headerlines', 4));
and if you have r2019b or later,
data = readmatrix([filename '.rpt'], 'headerlines', 4);
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Anshuman Pal
Anshuman Pal 2020 年 4 月 14 日
Thank you for suggesting readmatrix().
However, I still have a problem -- I want to use sscanf() to scrape the numbers 100, 101, 102, ... from the third header line:
X SHORT-1 N: 100 SHORT-1 N: 101 SHORT-1 N: 102 ...
Can you suggest a way of doing this?

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