Drop column of values using if function

I'm trying add some lines of code which drop columns that don't meet the condition. My values are 1500x28 matrix. Example:

if condition met

drop specific coloumn that meets condition

I know using A(:,3)=[] would drop column 3 but how do I not specify column number.

Thanks!

[Scott MacKenzie]

You can specify the column number as a variable. But, you'll need to set that variable to 3, perhaps through an if-else arrangement that includes the condition you allude to. More details would be helpful.

[Mahshad Rabiee]

Here is my code currently, i basically just want to ignore any columns in my plot where the percentage difference is less than 50%.

for i=1:length(mod_dirs)

%% ----------------------------------------------------MA data

% read the MomentArm (MA) data

MA_filename = [ base_dir mod_dirs{i} '\MA_MTL\' 'right_hip_muscle_flexion_MA.sto'];

MA = read_motionFile(MA_filename);

time = MA.data(:,2);

ma_flexion = MA.data(:,3:30);

ma_flexion_cm=ma_flexion*100;

mini_ma_flexion=min(ma_flexion_cm);

maxi_ma_flexion=max(ma_flexion_cm);

if (maxi_ma_flexion-mini_ma_flexion)<=(0.5*mini_ma_flexion);

ma_flexion_cm(:,:)=[];

continue;

end

[cycle_time,TN_ma_flexion]=normalise_data_points(time,ma_flexion_cm,t_cycle_start,t_cycle_end);

% create a plot of the MA of a selected muscle around the flex/ext axis

figure()

plot(cycle_time, TN_ma_flexion)

Answer 1

[Scott MacKenzie]

Set up a for-loop for your code, something like this.

time = MA.data(:,2);

for i=3:30
    ma_flexion = MA.data(:,i);
    ma_flexion_cm=ma_flexion*100;
    mini_ma_flexion=min(ma_flexion_cm);
    maxi_ma_flexion=max(ma_flexion_cm);

    if (maxi_ma_flexion-mini_ma_flexion)<=(0.5*mini_ma_flexion)
         ma_flexion_cm(:,i)=[];   
    end
end

The variable i will equal the column number whenever the condition is true, and the corresponding column will be deleted. Note: I deleted the semi-colon at the end of the if-expression.

[Mahshad Rabiee]

Thank you very much!!

[Mahshad Rabiee]

I'm getting an error: 'Matrix index is out of range for deletion'

[Mahshad Rabiee]

The for loop seems to have created just one column

[Scott MacKenzie]

Well, I said "something like this". I guess I'm not quite sure what you are trying to do. Maybe you need the loop setup like this:

ma_flexion = MA.data(:,3:30);
ma_flexion_cm=ma_flexion*100;

mini_ma_flexion=min(ma_flexion_cm); % array with 27 elements
maxi_ma_flexion=max(ma_flexion_cm); % array with 27 elements

for i=1:27
    if (maxi_ma_flexion(i)-mini_ma_flexion(i))<=(0.5*mini_ma_flexion(i))
         ma_flexion_cm(:,i)=[];   
    end
end

I think you can even do this without the for-loop. Try replacing the last five lines above with this:

conditionLogical = (maxi_ma_flexion-mini_ma_flexion)<=(0.5*mini_ma_flexion);
ma_flexion_cm(:,conditionLogical)=[];