So i wanted to add a column to this table.

Code for=> at the 2nd column i wanted to add data in form of an iteration.Starting with string 'Rest' from 1 to 202 then 202 to 204 will have sting 'active' then 205 to 407 will have 'rest', 408 to 610 will have 'active'.

Rest and active string in the second column for every 202nd iternation.

basically for 202 seconds its rest and next 202 seconds it active.... this is basically a paradim for fnirs brain signal.

Answer 1

[Guillaume]

Note that 1 to 203 having the same element makes that a half-period of 203, not 202.

Simple way to create a column vector that switches between two values at regular interval be;pw. I'm creating a table since as David said, you can't mix types in a matrix. I'm also storing 'rest' and 'active' as categorical, it's the most logical data type for this:

halfperiod = 203; %calculated however you want

values = categorical({'rest'; 'active'});
numperiods = ceil(numel(zz) / halfperiod / 2);  %last period may not be filled completely if numel(zz) is not a multiple of 2*halfperiod
filler = repmat(repelem(values, halfperiod), numperiods, 1);  %create repeated values numperiod times 
result = table(zz, filler(1:numel(zz)));
result.Properties.VariableNames = {'zz', 'state'}  %optional give good names to the table variables

No loop needed.

[CalebJones]

Worked like a breeze!

Thank you David K. and Guillaume, you guys are awesome.

[CalebJones]

Guillaume

I was refering to your same solution again. I'm getting an error now

Error using matlab.internal.builtinhelper.repelem (line 112)
Replication factors must be nonnegative integer-valued scalars or vectors.

This isn't working since my

halfperiod = 160; %changed
values = categorical({'rest'; 'left'; 'rest'; 'right'}); %changed.
numperiods = ceil(numel(zz) / halfperiod / 2);
filler = repmat(repelem(values, halfperiod), numperiods, 1);  
result = table(zz, filler(1:numel(zz)));
result.Properties.VariableNames = {'zz', 'state'}  

Other than that rest is the same. I have attached the mat file as well.

[Guillaume]

"Replication factors must be nonnegative integer-valued scalars or vectors."

The only way you can get this error with the above code is if halfperiod is negative, or non-integer, or a 2d matrix, so there must be some difference between the code you've posted and the code you're actually using.

Anyway, the easiest way for you to identify the problem is to use the debugger. Issue

dbstop if error

at the command prompt. Run your code and when it breaks into the debugger on error, look at the values of the variables.

Your attached mat file does not contain a variable called zz.

[CalebJones]

halfperiod = diff;%hardcode it to 160.
values = categorical({'rest'; 'left'; 'rest'; 'right'});
numperiods = ceil(numel(HbO_good_channel_onset) / halfperiod / 2);
filler = repmat(repelem(values, halfperiod), numperiods, 1);

This is my code. No need for zz, sorry about that.

At filler I get an error. Use the matlab attached previously. HbO_good_channel_onset is the matfile.

Guillaume

[Guillaume]

Again, if you get the error you state, halfperiod is not a scalar positive integer. It's not what you think it is, so use the debugger as I've explained to see what it actually is.

If I do:

halfperiod = 160;  %don't know what's in diff but it's certainly not 160.
values = categorical({'rest'; 'left'; 'rest'; 'right'});
numperiods = ceil(numel(HbO_good_channel_onset) / halfperiod / 2);
filler = repmat(repelem(values, halfperiod), numperiods, 1);

there is no error, as expected.

Note that using diff as a variable name is not a good idea as it will prevent you from using the very useful function of the same name.

[CalebJones]

So anyway to work around this problem? Guillaume

halfperiod = 175; %i miscalculated.  
values = categorical({'rest'; 'left'; 'rest'; 'right'});
numperiods = ceil(numel(HbO_good_channel_onset) / halfperiod / 2);
filler = repmat(repelem(values, halfperiod), numperiods, 1);

But issue still persists. Is it something to do with numperiods?

Any other solution?

[Guillaume]

I'm afraid you've lost me here, I'm not sure what the problem is anymore. Can you post together:

• the exact code you're using
• the matching data file
• the full text of the error

[CalebJones]

Guillaume

The issue was with the variable which was of the type floating point number.

halfperiod = int16(interval);

Interval is 175.000 so when I converted it to int16 issue was solved.

[Guillaume]

I would strongly recommend that you use

halfperiod = round(interval);  %or ceil(interval) or fix(interval) or floor(interval) depending on which rounding mode you want

instead of converting to int16.

To see what sort of trouble you can expect with your int16 conversion, see for example:

>> 800000 / int16(10)
ans = 
   int16
    32767

did you expect that?

[CalebJones]

Guillaume,

halfperiod = round(interval);

Does the job for me. Thank you.

Answer 2

[David K.]

So one big problem here is that you do not have a table. You have a matrix. And matrices cannot have strings and numbers in them. You have plenty of choices so here are 2.

If you want the matrix format you could instead say that active is 1 and rest is 0 and create the matrix as such:

x(1:201,1) = 0;
x(202:204,1) = 1;
x(205:407,1) = 0;
x(408:610,1) = 1;
FullMat = [zz , x];

If you want the words themselves you can do nearly the same thing:

x(1:201,1) = {'Rest'};
x(202:204,1) = {'active'};
x(205:407,1) = {'Rest'};
x(408:610,1) = {'active'};

This creates a cell of values. If you want them as the data type table you can then do

myTable = table(zz,x);

[CalebJones]

thanks a lot for your help.

is it possible to put in a loop??

[David K.]

probably, but what do you want the loop to do?

[Guillaume]

It's always possible to do things less efficiently, but why would you want to?

If the values in column 2 are based on the values in column 1, then it's very likely that a loop is not needed.

[CalebJones]

so basically every 202 seconds it has to switch from rest to active and so on..

1 to 203 will have continues value of 'Rest' and 204 to 406 will have value 'Active'...so on... in column two.

The value 202 isn't hardcoded it is calculated in a else, but that part is done and sorted.

Right now i want a way to put rest and active in column two.

If loops seems ineffecient pls suggest another way.

Psuedocode would really help.

Thank you

[David K.]

This may help you on your way:

flag = 0; % Start at rest
startVal = 1;
switchAmount = 202; % or whatever you call your calculated value

x(startVal:startVal+switchAmount,1) = flag;
% Could also do an if statement to do the words as shown in the original answer
flag = flag==0; % Flip flag between 1 and 0
startVal = startVal+switchAmount+1; % Update start val

Then if switchAmount is constant through a run you can put that bit in a loop for however many times you want it to. Or if you calculate switch amount multiple times you can put this after switch amount.

[CalebJones]

Thank you so so much.