How to apply conditional statements so as to select certain rows or columns on a given dataset.

How do I apply conditional statements so as to select certain rows or columns on a given dataset (like the one below)? For example, I would like to (1) display records with r only , (2) count records with + only .

Please note that the example of the data to be analyzed is given below. The data is separated by space. The data has 12 columns whose headings are; Event, time, from_Node, to_Node, Packet_Type, Packet_Size, Flags, Fid, Source_Address, Destination_Address, Sequence_Number and Packet_Id .

For example, + 0.155355 1 3 tcp 1500 ------- 0 0.0 3.0 2 3;

+ is an event,

0.155355 is time in secs,

1 is from_Node,

3 is to_Node,

tcp is Packet_Type, 1500 is Packet_Size,

 ------- are Flags,

0 is Fid,

0.0 is Source_Address,

3.0 is Destination_Address,

2 is Sequence_Number and

3 is Packet_Id.

_ _This is the data _

+ 0.155355 1 3 tcp 1500 ------- 0 0.0 3.0 2 3

- 0.160955 1 3 tcp 1500 ------- 0 0.0 3.0 2 3

r 0.170955 1 3 tcp 1500 ------- 0 0.0 3.0 1 2

r 0.178955 1 3 tcp 1500 ------- 0 0.0 3.0 2 3

+ 0.203632 1 3 tcp 1500 ------- 0 0.0 3.0 3 6

- 0.203632 1 3 tcp 1500 ------- 0 0.0 3.0 3 6

+ 0.206032 1 3 tcp 1500 ------- 0 0.0 3.0 4 7

+ 0.211632 1 3 tcp 1500 ------- 0 0.0 3.0 5 8

Thank you

[Manduna Watson]

This works. Thank you very much.

Answer 1

[Cedric]

Here is another approach

 content = fileread( 'myData.txt' ) ;
 nPlus   = sum( content == '+' ) ;
 rRows   = regexp( content, '(?<=(^|\n)r )[^\r\n]*', 'match' ) ;

with that you get

 >> nPlus
 nPlus =
         4

and

 >> fprintf( '%s\n', rRows{:} ) ;

    0.170955 1 3 tcp 1500 ------- 0 0.0 3.0 1 2
    0.178955 1 3 tcp 1500 ------- 0 0.0 3.0 2 3

PS: I can explain the regexp pattern if anyone is interested. Just let me know.

EDIT: I slightly modified the call to regexp to manage cases with/without header.

[Sara]

If you are volunteering to explain regexp I'll listen, I haven't understood it enough to use it successfully yet!

[Cedric]

The pattern matches the following

• as many characters as possible which are different from \r and |

[Manduna Watson]

Using the same technique, how can I, for example,

(A): select and display data with + , 3 , and tcp only .

(B): select and add data with + , 3 , tcp and 3.0 only

Answer 2

[Sara]

clc
clearvars

% Read file
filecontent = cell(1000,1);
k = 0;
fid = fopen('mydata.txt','r');
while 1
    t = fgetl(fid);
    if(~ischar(t)),break,end
    k = k + 1;
    filecontent{k} = t;
end
filecontent = filecontent(1:k);
fclose(fid);

% To get only the first character
fid = fopen('mydata.txt','r');
t = textscan(fid,'%s%*[^\n]');t = t{1};
fclose(fid);

% r data
index_r = find(strcmp(t,'r')==1);
filecontent(index_r)

% + data
index_plus = find(strcmp(t,'+')==1);
numel(index_plus)

[Manduna Watson]

Perfect solution. Thank you

[Manduna Watson]

I have been going through your perfect answer. I however had challenges of utilising the extracted data (filecontent). For example, how can I display and use the first (event) and second (time)column only ? The objective is to find the position where r appears , and then plot it against column 2 ).

For example; from the data above, r appears on position 3, 8, 17, 19 etc. The corresponding time values for r are 0.12028, 0.17096, 0.17896, 0.22163 .

In short, I want to have something like this;

event = [3,8, 17,19,20]

timeReceived =[0.12028, 0.17096, 0.17896, 0.22163, 0.22963]

Thank you

[Sara]

Unde % r data, try this and see if it does what you like. ps: 'r' appears only on line 3 and 4 for the data posted.

index_r = find(strcmp(t,'r')==1);
f = filecontent(index_r);
value = cellfun(@(t)sscanf(t,'%*s %f%*[^\n]',...   
          numel(index_r)),f,'UniformOutput',0);
value = cell2mat(value);
plot(index_r,value,'o')

[Manduna Watson]

Thank you, it works

[Manduna Watson]

Using the same technique, how can I, for example,

(A): select and display data with + , 3 , and tcp only .

(B): select and add data with + , 3 , tcp and 3.0 only