How can I extract the last rows of specific columns of a text file

Please, I have a text file contains three columns I need to extract the last rows of the third and forth columns only and write them into a text file. for example, from the text file attached the result needs to be written in a text file. it should return:

1.87 36

157 35

1.88 37

1.36 48

1.73 78

1.99 100

Many thanks

[Jan]

There is no attached file.

[ND]

Sorry this is the file, Thanks

Answer 1

[Thorsten]

Read the data from file, ignoring 1 header line:

 data = cell2mat(textscan(fopen('a.txt'), '%f%f%f', 'headerlines', 1));

Find the last position for each sequence in column 2. The last position is the position where the data changes, i.e., where the difference is > 0. Add 1 to the end get the last position for the last sequence:

idx = find([diff(data(:,2)); 1] > 0);

Now we have the position of the last entry of each sequence in ind. Since we want the last n elements of a sequence, we use the entry x minus n+1, so x -2 in case of n = 3. For the i'th sequence, we want to extract data(ind(i)-2:ind(i), 3). Instead of using a for-loop, we use arrayfun to work on the ind array:

d3 = arrayfun(@(x) (data(x-2:x,3)), idx, 'UniformOutput', false);

The final step is to write the numbers to a file:

 dlmwrite('b.txt', d3)

[ND]

Many thanks Thorsten Sorry, what about if I do not have headers ,( just data)?

[Thorsten]

Just don't skip the ", 'headerlines', 1" part.

Answer 2

[TastyPastry]

Open the file

 fid = fopen('your file name.txt');

Skip the header

 fgetl(fid);

Use textscan()

 myOutput = textscan(fid,'%d %d %d');

It will return a cell array containing all the numerical data, just ignore the first two columns.

[ND]

Sorry that is not what I need. For example, a text file has the following:

Bar No increment No Variable

1 1 0

2 1 3

1 2 4

2 2 5

1 2 6

2 2 9

I need to extract just the last variable values(column 3) of each increment

Returns one column written in a text file as :

0

3

6

9