Splitting of a column to multiple columns

Hi,

If I have a 100 x 1 column of numbers between -1 to 100 and i want to eliminate the 0's and negative numbers, then split the column into 10 rows each and call each row a given name so as to plot them against each other.

Could you advise how to do this, thanks

[jahanzaib ahmad]

when u will eliminate negative numbers or zeros with what number u want to replace those null values ? and if u just elimenate zeros or negative number e.g u are left with 95 number .how that can be equally split ?

[Olu B]

I want to replace the numbers I eliminate with 1 then split the column to multiple columns.

Thanks

[jahanzaib ahmad]

replace 0 or negative values with 1

n=(-1+(2-(-1)).*rand(100,1));

m=n;

for i=1:length(n)

if n(i)<0

n(i)=1;

end

end

[Stephen23]

Simpler:

n = max(1,n)

or

n(n<1) = 1

[jahanzaib ahmad]

sir @Stephen Cobeldick whats the easy way to split 100x1 into 10 columns of 10x1

a=n(1:10,:);b=n(11:20,:);c=n(21:30,:);d=n(31:40,:);e=n(41:50,:);f=n(51:60,:);g=n(61:70,:);h=n(71:80,:);i=n(81:90,:);

j=n(91:100,:);

[Stephen23]

" whats the easy way to split 100x1 into 10 columns of 10x1 "

There is no easy way to do that "automatically". In fact, you should avoid doing that (unless you want to force yourself into writing slow, complex, buggy code which is hard to debug).

The best solutions would be to either reshape the array (e.g. as Renato shows), or split the data into a cell array (e.g. using num2cell or mat2cell).

Answer 1

[Renato SL]

After doing what Stephen Cobeldick suggested in the comments, I believe this would do it.

n2 = reshape(n,[],10);

[Olu B]

Thank you.

I would like to ask an additional question.

for example I have a column of 1000 by 1 matrix and I want to split it into 10 columns each, and each column should have 10 rows. So that after the 10th column and 10th row for the first round of splits, the split would start again from the 1st row and add the next 10 rows.

To clarify: 10th column would have 10 rows of 91 - 100, thereafter the next split would start from the 1st column with another 10 rows starting from 101 - 110 and so on till it gets to 1000

Thanks

[Renato SL]

From what I understand, this time you initially have one (1000 x 1) matrix and in the end, you want to have 10 of (10 x 10) matrix.

Is this correct?

[Olu B]

Yes that is correct, however I want to have 10 of (10 by 10) matrix till 1000, so each of the 10 columns will have 100 rows, but next split after the first split of 10 by 10 would start from the 1st column with another 10 rows starting from 101 - 110 and so on till it gets to 1000.

I think a loop would be needed such that 1st column will be (1 -10) and 10th column ( 91 -100), then start from 1st column with the next 10 rows of (101 - 110), 2nd column with next 10 rows of ( 111 - 120) ...... and 10th column with 10 rows of (191 - 200) and so on.

[Renato SL]

For that, I recommend using reshape function again. I think it would look like this.

Say you have matrix n (1000 by 1) originally, then

n = [1:1000]';
n2 = reshape(n,10,10,10);

so that n would be reshaped into a (10 by 10 by 10) matrix. The first 100 entries then would look like

n2(:,:,1)

ans =

     1    11    21    31    41    51    61    71    81    91
     2    12    22    32    42    52    62    72    82    92
     3    13    23    33    43    53    63    73    83    93
     4    14    24    34    44    54    64    74    84    94
     5    15    25    35    45    55    65    75    85    95
     6    16    26    36    46    56    66    76    86    96
     7    17    27    37    47    57    67    77    87    97
     8    18    28    38    48    58    68    78    88    98
     9    19    29    39    49    59    69    79    89    99
    10    20    30    40    50    60    70    80    90   100
    

The second 100

n2(:,:,2)

ans =

   101   111   121   131   141   151   161   171   181   191
   102   112   122   132   142   152   162   172   182   192
   103   113   123   133   143   153   163   173   183   193
   104   114   124   134   144   154   164   174   184   194
   105   115   125   135   145   155   165   175   185   195
   106   116   126   136   146   156   166   176   186   196
   107   117   127   137   147   157   167   177   187   197
   108   118   128   138   148   158   168   178   188   198
   109   119   129   139   149   159   169   179   189   199
   110   120   130   140   150   160   170   180   190   200
   

and so on.

Then to keep each 100 as separate matrices, simply do something like

n100 = n2(:,:,1);
n200 = n2(:,:,2);
%and so on

[Olu B]

Thanks for your help. This works

[Stephen23]

@Olu B: note that splitting up your data makes it harder to work with.

Using indexing is much simpler.