I am attempting to write a script to import a large .txt file containing multiple columns of data into seperate variables within Matlab.
I have reached a stage where I have my 7 datasets:
Var1= 3230 x 1 double
Var2= 3230 x 1 double
Var3= 3230 x 1 double
Var4= 3230 x 1 double
Var5= 3230 x 1 double
Var6= 3230 x 1 double
Var7= 3230 x 1 double
and an array containing all of the variable names in different cells:
nameArray= 1 x 7 cell
My question is: how do I create variables with the same names as those within nameArray and subsequently populate them with data from my datasets?
You have three options:
Use assignin:
assignin('caller', nameArray{1}, Var1)
assignin('caller', nameArray{2}, Var2)
...
This will create a variable with name nameArray{1} and value Var1 in the namespace of the caller.
Build a struct:
x = struct()
x.(nameArray{1}) = Var1
...
This builds a struct with dynamically assigned fields.
As #Scott suggests in his answer: Use readtable:
T = readTable('mydatafile.txt')
This yields a similar result as option 2. But T is of type table and not struct. Tables are availble in Matlab versions R2013b and newer.
And of course you should use a loop
You might want to consider using T = readTable('mydatafile.txt'). This allows you to load a file with seperate columns and access those colums using their column name, for example like this: T.MyFirstColumn. See the manual on readtable for some examples.
Related
I am trying to split a string variable into multiple dummy coded variables. I used these sources to get an idea of how one would achieve this task in SPSS:
https://www.ibm.com/support/pages/making-multiple-string-variables-single-multiply-coded-field
https://www.spss-tutorials.com/spss-split-string-variable-into-separate-variables/
But when I try to adapt the first one to my needs or when I try to convert the second one to a macro, I fail.
In my dataset I have (multiple) variables that contain a comma seperated string that represents different combinations of selected items (as well as missing values). For each item of a specific variable I want to create a dummy variable. If the item was selected, it should be represented with a 1 in the new dummy variable. If it was not selected, that case should be represented with a 0.
Different input variables can contain different numbers of items.
For example:
ID
VAR1
VAR2
DMMY1_1
DMMY1_2
DMMY1_3
1
1, 2
8
1
1
0
2
1
1, 3
1
0
0
3
3, 1
2, 3, 1
1
0
1
4
2, 8
0
0
0
Here is what I came up with so far ...
* DEFINE DATA.
DATA LIST /ID 1 (F) VAR1 2-5 (A) VAR2 6-12 (A).
BEGIN DATA
11, 28
21 1, 3
33, 12, 3, 1
4 2, 8
END DATA.
* MACRO SYNTAX.
* DEFINE VARIABLES (in the long run these should/will be inside the macro function, but for now I will leave them outside).
NUMERIC v1 TO v3 (F1).
VECTOR v = v1 TO v3.
STRING #char (A1).
DEFINE split_var(vr = TOKENS(1)).
!DO !#pos=1 !TO char.length(!vr).
COMPUTE #char = char.substr(!vr, !#pos, 1).
!IF (!#char !NE "," !AND !#char !NE " ") !THEN
COMPUTE v(NUMBER(!#char, F1)) = 1.
!IFEND.
!DOEND.
!ENDDEFINE.
split_var vr=VAR1.
EXECUTE.
As I got more errors than I can count, it's hard to narrow down my problem. But I think the problem has something to do with the way I use the char.length() function (and I am a bit confused when to use the bang operator).
If anyone has some insights, I would really appreciate some help :)
There is a fundamental issue to understand about SPSS macro - the macro does not read or interact in any way with the data. All the macro does is manipulate text to write syntax. The syntax created will later work on the actual data when you run it.
So, for example, Your first error is using char.length(!vr) within the syntax. You are trying to get the macro to read the data, calculate the length and use, but that simply can't be done - the macro can only work with what you gave it.
Another example in your code: you calculate #char and then try to use it in the macro as !#char. So that obviously won't work. ! precedes only macro functions or arguments. #char, in your code, is neither, and it can't become one - can't read the data into the macro...
To give you a litte push forward: I understand you want the macro loop to run a different number of times for each variable, but you can't use char.length(!vr). I suggest instead have the macro loop as many times as necessary to be sure you can deal with the longest variable you'll need to work with.
And another general strategy hint - first, create syntax to deal with one specific variable and one specific delimiter. Once this works, start working on a macro, keeping in mind that the only purpose of the macro is to recreate the same working syntax, only changing the parameters of variable name and delimiter.
With my new understanding of the SPSS macro logic (thanks to #eli-k) the problem was quite easy to solve. Here is the working solution.
* DEFINE DATA.
DATA LIST /ID 1 (F) VAR1 2-5 (A) VAR2 6-12 (A).
BEGIN DATA
11, 28
21 1, 3
33, 12, 3, 1
4 2, 8
END DATA.
* DEFINE MACRO.
DEFINE #split_var(src_var = !TOKENS(1)
/dmmy_var_label = !DEFAULT(dmmy) !TOKENS(1)
/dmmy_var_lvls = !TOKENS(1))
NUMERIC !CONCAT(!dmmy_var_label,1) TO !CONCAT(!dmmy_var_label, !dmmy_var_lvls) (F1).
VECTOR #dmmy_vec = !CONCAT(!dmmy_var_label,1) TO !CONCAT(!dmmy_var_label, !dmmy_var_lvls).
STRING #char (A1).
LOOP #pos=1 TO char.length(!src_var).
COMPUTE #char = char.substr(!src_var, #pos, 1).
DO IF (#char NE "," AND #char NE " ").
COMPUTE #index = NUMBER(#char, F1).
COMPUTE #dmmy_vec(#index) = 1.
END IF.
END LOOP.
RECODE !CONCAT(!dmmy_var_label,1) TO !CONCAT(!dmmy_var_label, !dmmy_var_lvls) (SYSMIS=0) (ELSE=COPY).
EXECUTE.
!ENDDEFINE.
* CALL MACRO.
#split_var src_var=VAR2 dmmy_var_lvls=8.
I'd like to write several messages and tables on the same .txt file.
For example:
x=[23.9,10.9,8.9,14.2]
y=[9.83,8.04,7.47,8.32]
file=fopen('Results.txt','wt');
fprintf(file,'Results1\n');
fprintf(file,'%.2f %.2f\r\n',x,y);
fprintf(file,'Results2\n');
fclose(file);
I get this result as .txt:
Results1
23.90 10.90
8.90 14.20
9.83 8.04
7.47 8.32
Results2
But I should get this one:
Results1
23.90 9.83
10.90 8.04
8.90 7.47
14.20 8.32
Results2
Instead of fprintf(file,'%.2f %.2f\r\n',x,y);), I was trying to use:
ResultsTable2 = table(x,y);
writetable(file,ResultsTable2);
but didn't succeed. How to write the required .txt file?
Careful examination of your output shows that all the elements of x were printed before all the elements of y.
The documentation confirms that this is the expected behavior. Check out this example
A1 = [9.9, 9900];
A2 = [8.8, 7.7 ; ...
8800, 7700];
formatSpec = 'X is %4.2f meters or %8.3f mm\n';
fprintf(formatSpec,A1,A2)
X is 9.90 meters or 9900.000 mm
X is 8.80 meters or 8800.000 mm
X is 7.70 meters or 7700.000 mm
Even though the arguments to fprintf are in the order A1, A2. It first prints all the values from A1, and then it prints all the values from A2 going in single index order.
Therefore, if you want to alternate values from x and y during printing, you need to interleave them in a new variable. There are several possible ways to do so.
One example,
XY = reshape([x;y], 1, []);
Then everything should print as expected
fprintf(file, '%.2f %.2f\r\n', XY);
% or if you want to print to command window
% fprintf('%.2f %.2f\r\n', XY);
23.90 9.83
10.90 8.04
8.90 7.47
14.20 8.32
The correct answer for how to output data with fprintf is given by Cecilia: each argument will be iterated completely through in the order it appears in the argument list, so you have to combine the data into one matrix argument that will be iterated through column-wise to generate the desired output.
You also mentioned trying to use a table and the writetable function, so I though I'd add the correct way to do that in case you were curious:
ResultsTable2 = table(x(:), y(:)); % Pass data as column vectors
writetable(ResultsTable2, 'Results.txt', 'WriteVariableNames', false);
I am trying to define the following function in MATLAB:
file = #(var1,var2,var3,var4) ['var1=' num2str(var1) 'var2=' num2str(var2) 'var3=' num2str(var3) 'var4=' num2str(var4)'];
However, I want the function to expand as I add more parameters; if I wanted to add the variable vark, I want the function to be:
file = #(var1,var2,var3,var4,vark) ['var1=' num2str(var1) 'var2=' num2str(var2) 'var3=' num2str(var3) 'var4=' num2str(var4) 'vark=' num2str(vark)'];
Is there a systematic way to do this?
Use fprintf with varargin for this:
f = #(varargin) fprintf('var%i= %i\n', [(1:numel(varargin));[varargin{:}]])
f(5,6,7,88)
var1= 5
var2= 6
var3= 7
var4= 88
The format I've used is: 'var%i= %i\n'. This means it will first write var then %i says it should input an integer. Thereafter it should write = followed by a new number: %i and a newline \n.
It will choose the integer in odd positions for var%i and integers in the even positions for the actual number. Since the linear index in MATLAB goes column for column we place the vector [1 2 3 4 5 ...] on top, and the content of the variable in the second row.
By the way: If you actually want it on the format you specified in the question, skip the \n:
f = #(varargin) fprintf('var%i= %i', [(1:numel(varargin));[varargin{:}]])
f(6,12,3,15,5553)
var1= 6var2= 12var3= 3var4= 15var5= 5553
Also, you can change the second %i to floats (%f), doubles (%d) etc.
If you want to use actual variable names var1, var2, var3, ... in your input then I can only say one thing: Don't! It's a horrible idea. Use cells, structs, or anything else than numbered variable names.
Just to be crytsal clear: Don't use the output from this in MATLAB in combination with eval! eval is evil. The Mathworks actually warns you about this in the official documentation!
How about calling the function as many times as the number of parameters? I wrote this considering the specific form of the character string returned by your function where k is assumed to be the index of the 'kth' variable to be entered. Array var can be the list of your numeric parameters.
file=#(var,i)[strcat('var',num2str(i),'=') num2str(var) ];
var=[2,3,4,5];
str='';
for i=1:length(var);
str=strcat(str,file(var(i),i));
end
If you want a function to accept a flexible number of input arguments, you need varargin.
In case you want the final string to be composed of the names of your variables as in your workspace, I found no way, since you need varargin and then it looks impossible. But if you are fine with having var1, var2 in your string, you can define this function and then use it:
function str = strgen(varargin)
str = '';
for ii = 1:numel(varargin);
str = sprintf('%s var%d = %s', str, ii, num2str(varargin{ii}));
end
str = str(2:end); % to remove the initial blank space
It is also compatible with strings. Testing it:
% A = pi;
% B = 'Hello!';
strgen(A, B)
ans =
var1 = 3.1416 var2 = Hello!
I have a long list of variables in my workspace.
First, I'm finding the potential variables I could be interested in using the who function. Next, I'd like to loop through this list to find the size of each variable, however who outputs only the name of the variables as a string.
How could I use this list to refer to the values of the variables, rather than just the name?
Thank you,
list = who('*time*')
list =
'time'
'time_1'
'time_2'
for i = 1:size(list,1);
len(i,1) = length(list(i))
end
len =
1
1
1
If you want details about the variables, you can use whos instead which will return a struct that contains (among other things) the dimensions (size) and storage size (bytes).
As far as getting the value, you could use eval but this is not recommended and you should instead consider using cell arrays or structs with dynamic field names rather than dynamic variable names.
S = whos('*time*');
for k = 1:numel(S)
disp(S(k).name)
disp(S(k).bytes)
disp(S(k).size)
% The number of elements
len(k) = prod(S(k).size);
% You CAN get the value this way (not recommended)
value = eval(S(k).name);
end
#Suever nicely explained the straightforward way to get this information. As I noted in a comment, I suggest that you take a step back, and don't generate those dynamically named variables to begin with.
You can access structs dynamically, without having to resort to the slow and unsafe eval:
timestruc.field = time;
timestruc.('field1') = time_1;
fname = 'field2';
timestruc.(fname) = time_2;
The above three assignments are all valid for a struct, and so you can address the fields of a single data struct by generating the field strings dynamically. The only constraint is that field names have to be valid variable names, so the first character of the field has to be a letter.
But here's a quick way out of the trap you got yourself into: save your workspace (well, the relevant part) in a .mat file, and read it back in. You can do this in a way that will give you a struct with fields that are exactly your variable names:
time = 1;
time_1 = 2;
time_2 = rand(4);
save('tmp.mat','time*'); % or just save('tmp.mat')
S = load('tmp.mat');
afterwards S will be a struct, each field will correspond to a variable you saved into 'tmp.mat':
>> S
S =
time: 1
time_1: 2
time_2: [4x4 double]
An example writing variables from workspace to csv files:
clear;
% Writing variables of myfile.mat to csv files
load('myfile.mat');
allvars = who;
for i=1:length(allvars)
varname = strjoin(allvars(i));
evalstr = strcat('csvwrite(', char(39), varname, '.csv', char(39), ', ', varname, ')');
eval(evalstr);
end
Many near-solutions are online, but nothing exact...
I am building a data matrix vector-by-vector:
OutputMatrix(NextSubject,:)=[OutputVector]
I need to lead each row with the name of the data being processed in that loop. The name has the form:
12345.dat
So if OutputVector=[1 2 3 4] the output should look like:
12345.dat 1 2 3 4
I have tried dozens of solutions, but a few examples:
{char(Filename(i).name) OutputVector}
{strcat((Filename(i).name) OutputVector)}
[Filname(i).name OutputVector]
Any help? Please :)
You can't store a string and a vector in a matrix. However, you can do that in a cell.
So you might consider doing:
OutputCell(NextSubject,:) = { Filename(i).name OutputVector };
The curly braces denote that you are storing the object as a cell.
Often though it is better to store strings and number separately. Something like:
OutputMatrix = [];
OutputFile = {};
...
OutputMatrix(NextSubject,:) = OutputVector;
OutputFile{NextSubject} = Filename(i).name;
Then if you access or select rows from output matrix, use the same index for the cell array:
foo(OutputMatrix(index,:), OutputFile(index))