I have data stored in variable data.
data =
[43.98272955 39.55809471;
-49.51656799 28.57164726;
-9.475861028 -44.31264255;
27.14884251 2.603921223;
-2.914496888 7.864022006;
4.093025860 4.816211687;
-12.11007479 5.797539648;
-1.653535904 -12.49864642;
5.978990391 1.229984916;
0.9837133282 -2.001124423;
5.674977844 6.323209942;
-9.574459589 3.696791663;
0.3410452503 -7.338955191]
but need use only data corresponding to multiple numbers of x.
Example:
if x = 3,
want store only multiple rows of 3, so
newdata = [-9.475861028 -44.31264255;
4.093025860 4.816211687;
5.978990391 1.229984916;
-9.574459589 3.696791663]
how do I do that?
P.S I would use the command textscan.
this is straightforward with indexing:
newData = data(3:3:end,:)
If I understood the question correctly:
data(x:x:length(data),:)
You could just do just scan it row by row using the mod (modulo) function to extract rows corresponding to the desired multiples. For example:
x=3;
newdata=[];
for k=1:size(data,1)
if mod(k,x)==0
newdata=[newdata; data(k,:)];
end
end
Related
I have a problem I hope you can help me with.
I have imported a large dataset (200000 x 5 cell) in Matlab that has the following structure:
'Year' 'Country' 'X' 'Y' 'Value'
Columns 1 and 5 contain numeric values, while columns 2 to 4 contain strings.
I would like to arrange all this information into a variable that would have the following structure:
NewVariable{Country_1 : Country_n , Year_1 : Year_n}(Y_1 : Y_n , X_1 : X_n)
All I can think of is to loop through the whole dataset to find matches between the names of the Country, Year, X and Y variables combining the if and strcmp functions, but this seems to be the most ineffective way of achieving what I am trying to do.
Can anyone help me out?
Thanks in advance.
As mentioned in the comments you can use categorical array:
% some arbitrary data:
country = repmat('ca',10,1);
country = [country; repmat('cb',10,1)];
country = [country; repmat('cc',10,1)];
T = table(repmat((2001:2005)',6,1),cellstr(country),...
cellstr(repmat(['x1'; 'x2'; 'x3'],10,1)),...
cellstr(repmat(['y1'; 'y2'; 'y3'],10,1)),...
randperm(30)','VariableNames',{'Year','Country','X','Y','Value'});
% convert all non-number data to categorical arrays:
T.Country = categorical(T.Country);
T.X = categorical(T.X);
T.Y = categorical(T.Y);
% here is an example for using categorical array:
newVar = T(T.Country=='cb' & T.Year==2004,:);
The table class is made for such things, and very convenient. Just expand the logic statement in the last line T.Country=='cb' & T.Year==2004 to match your needs.
Tell me if this helps ;)
I have a data (matrix) with 3 columns : DATA=[ID , DATE, Value]
I want to filter my data by ID for example DATAid1= DATA where ID==1 and so on ..
for that I write this code in MATLAB
load calibrage_capteur.mat
data = [ID ,DATE , Valeur]
minid = min(data(:,1));
maxid = max(data(:,1));
for i=minid:maxid
ind=find(data(:,1) == i)
dataID = [ID(ind) ,DATE(ind) , Valeur(ind)]
end
As a result he register the last value in this example the max ID=31 so he register dataId31. Now I need how to save the variable each iteration. How can I do this?
You will want to use a cell array to hold your data rather than saving them as independent variables that are named based upon the ID.
data_by_ID = cell();
ids = minid:maxid;
for k = 1:numel(ids)
data_by_ID{k} = data(data(:,1) == ids(k),:);
end
Really though, depending on what you're doing with it, you can use data all of the time since all operations are going to be faster on a numeric matrix than they are on a cell array.
%// Do stuff with data ID = 10
do_stuff(data(data(:,1) == 10, :));
Update
If you absolutely must name your variables you could do the following (but please don't do this and use one of the methods above).
for k = 1:numel(ids)
eval(['dataId', num2str(ids(k)), '= data(k,:);']);
end
Your question is a bit unclear but it sounds like you simply want to save the result at each iteration of the for loop.
I'm assuming min and max id are arbitrary and not necessarily the variable you are trying to index on.
kk = min_id:max_id;
dataID=nan(size(kk));
for ii = 1:numel(kk)
ind=find(data(:,1) == kk(ii))
dataID(kk) = [ID(ind) ,DATE(ind) , Valeur(ind)]
end
This is better than indexing by min_id or max_id since it isn't clear that min_id starts at at 1 (maybe it starts at 0, or something else.)
I currently have the deck of cards coded, but it is unshuffled. This is for programming the card game of War if it helps. I need to shuffle the deck, but whenever I do, it will only shuffle together the card numbers and the suits, not the full card. For example, I have A identified as an ace and the suits come after each number. A normal card would be "AH" (an ace of hearts) or "6D" (a six of diamonds). Instead, it will output "5A" as one of the cards, as in a 5 of aces. I don't know how to fix this, but the code that I currently have is this:
card_nums = ('A23456789TJQK')';
card_suits = ('HDSC')';
unshuffled_deck = [repmat(card_nums,4,1),repmat(card_suits,13,1)];
disp(unshuffled_deck)
shuffled_deck = unshuffled_deck(randperm(numel(unshuffled_deck)));
disp(shuffled_deck)
I would appreciate any help with this, and thank you very much for your time!
You're creating a random permutation of all of the elements from both columns of unshuffled_deck combined. Instead you need to create a random permutation of the rows of unshuffled_deck:
shuffled_deck = unshuffled_deck(randperm(size(unshuffled_deck,1)),:);
The call to size gives you the number of rows in the deck array, then we get a random permutation of the row indices, and copy the row (value, suit) as a single entity.
Here's a version using a structure array in response to #Carl Witthoft's comment. I was afraid it would add too much complexity to the solution, but it really isn't bad:
card_nums = ('A23456789TJQK')';
card_suits = ('HDSC')';
deck_nums = repmat(card_nums,4,1);
deck_suits = repmat(card_suits,13,1);
cell_nums = cellstr(deck_nums).'; %// Change strings to cell arrays...
cell_suits = cellstr(deck_suits).'; %// so we can use them in struct
%// Construct a struct array with fields 'value' and 'suit'
unshuffled_deck = struct('value',cell_nums,'suit',cell_suits);
disp('unshuffled deck:');
disp([unshuffled_deck.value;unshuffled_deck.suit]);
%// Shuffle the deck using the number of elements in the structure array
shuffled_deck = unshuffled_deck(randperm(numel(unshuffled_deck)));
disp('shuffled deck:');
disp([shuffled_deck.value; shuffled_deck.suit]);
Here's a test run:
unshuffled deck:
A23456789TJQKA23456789TJQKA23456789TJQKA23456789TJQK
HDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSCHDSC
shuffled deck:
4976TT93KTJQJATK953A75QA82Q6226K5J784J4A3372486K859Q
CHSSSHCDSCSSHDDCDSHHCDHSDDCDHCCHHCHHHDDCSCDSSCHDSCSD
To access an individual card, you can do:
>> shuffled_deck(2)
ans =
scalar structure containing the fields:
value = 9
suit = H
Or you can access the individual fields:
>> shuffled_deck(2).value
ans = 9
>> shuffled_deck(2).suit
ans = H
Unfortunately, I don't know of any way to simply index the struct array and get, for instance, 9H as you would in a regular array using disp(shuffled_deck(2,:)). In this case, the only option I know of is to explicitly concatenate each field:
disp([shuffled_deck(2).value,shuffled_deck(2).suit]);
In MatLab, I have several data vectors that are in text. For example:
speciesname = [species1 species2 species3];
genomelength = [8 10 5];
gonometype = [RNA DNA RNA];
I realise that to make a plot, arrays must be numerical. Is there a quick and easy way to assign unique entries in an array a number, for example so that RNA = 1 and DNA = 2? Note that some arrays might not be binary (i.e. have more than two options).
Thanks!
So there is a quick way to do it, but im not sure that your plots will be very intelligible if you use numbers instead of words.
You can make a unique array like this:
u = unique(gonometype);
and make a corresponding number array is just 1:length(u)
then when you go through your data the number of the current word will be:
find(u == current_name);
For your particular case you will need to utilize cells:
gonometype = {'RNA', 'DNA', 'RNA'};
u = unique(gonometype)
u =
'DNA' 'RNA'
current = 'RNA';
find(strcmp(u, current))
ans =
2
We've got an array of values, and we would like to create another array whose values are not in the first one.
Example:
load('internet.mat')
The first column contains the values in MBs, we have thought in something like:
MB_no = setdiff(v, internet(:,1))
where v is a 0 vector whose length equals to the number of rows in internet.mat. But it just doesn't work.
So, how do we do this?
You need to specify the range of possible values to define what values are not in internet . Say the range is v = 1:10 then setdiff(v,internet(:,1)) will give you the values in 1:10 that are not in the first column of internet.
It seems as if you don't want the first column.
You can simply do:
MB_no=internet(:,2:end);
assuming internet(:,1) has only positive integers and you wish to find which are the integers in [1,...,max( internet(:,1) )] that do not appear in that range you can simply do
app = [];
app( internet(:,1) ) = 1;
MB_no = find( app == 0 );
This is somewhat like bucket sort.