I have an excel file that I grab by:
ds = dataset('XLSFile',fullfile('file path here', 'waterReal.xlsx'))
It looks like this:
I want each column in its own numeric array though! Like how when I load an example dataset: load carsmall, I get a bunch of individual numeric arrays. But I can't figure out how to do that.
I can do this individually by writing:
A = ds.TEMP, B = ds.PROD, ...
Bu what if I had BIG excel file? What then?
You can convert a dataset to a struct or a cell like this:
To struct:
s = dataset2struct(ds, 'AsScalar',true)
To cell:
fnames = fieldnames(ds);
c = cell(1, numel(fnames));
for i = 1:numel(fnames)
c{i} = ds.(fnames{i});
end
By the way: use tables instead of datasets. They're newer and better. Use the readtable function to read your Excel file into a table. And tables are nicer enough that you might not want to bother converting them into a simpler cell array, because you can just grab the columns out with t{:,i} where t is your table and i is the index of the column you want.
Related
I have a table named cellName of size 10000*1. Each entry is a character string of cell names. Each cell name is of different length.
And I want to coerce it into a vector with 10000 elements. How can i do that in matlab? It should be very easy as that in r but i didn't find such command in matlab.
OR: I used readtable to load the 10000*1 table from csv file at the very beginning. It would be great if I can directly read the 10000*1 entries as a single vector too. This is what i did at first.
cellName = readtable('cell.csv');
cellName=cellName(1:10000,1);
Thank you in advance!
Clear example: A is a table of 5*1.
A= apple
banana
pear
peach
watermelon
And i want to coerce A into a vector of 5 elements: A=[apple,banana,pear,peach,watermelon] instead of a table
If a character cell array is what you want, I may have your answer. I also suggest you to read how to access data in a table.
readtable returns a Matlab table data type when succeeded. The table can be accessed like struct with your column name as the fieldname, or be indexed by {} operator like you would access a cell array.
In your example, assuming A is the return value of readtable and your
A = table({'apple','banana','pear','peach','watermelon'}','variableNames',{'cellName'})
Then you can either call
cellName = A.cellName
or
cellName = A{:,1}
to get your cell array.
I have a dataset that I would like to categorise and store in a structure based on the value in one column of the dataset. For example, the data can be categorised into element 'label_100', 'label_200' or 'label_300' as I attempt below:
%The labels I would like are based on the dataset
example_data = [repmat(100,1,100),repmat(200,1,100),repmat(300,1,100)];
data_names = unique(example_data);
%create a cell array of strings for the structure fieldnames
for i = 1:length(data_names)
cell_data_names{i}=sprintf('label_%d', data_names(i));
end
%create a cell array of data (just 0's for now)
others = num2cell(zeros(size(cell_data_names)));
%try and create the structure
data = struct(cell_data_names{:},others{:})
This fails and I get the following error message:
"Error using struct
Field names must be strings."
(Also, is there a more direct method to achieve what I am trying to do above?)
According to the documentation of struct,
S = struct('field1',VALUES1,'field2',VALUES2,...) creates a
structure array with the specified fields and values.
So you need to have each value right after its field name. The way you are calling struct now is
S = struct('field1','field2',VALUES1,VALUES2,...)
instead of the correct
S = struct('field1',VALUES1,'field2',VALUES2,...).
You can solve that by concatenating cell_data_names and others vertically and then using {:} to produce a comma-separated list. This will give the cells' contents in column-major order, so each field name fill be immediately followed by the corresponding value:
cell_data_names_others = [cell_data_names; others]
data = struct(cell_data_names_others{:})
I have a large amount of .csv files from my experiments (200+) and previously I have been reading them in seperately and also for later steps in my data handling this is tedious work.
co_15 = csvread('CO_15K.csv',5,0);
co_25 = csvread('CO_25K.csv',5,0);
co2_15 = csvread('CO2_15K.csv',5,0);
co2_80 = csvread('CO2_80K.csv',5,0);
h2o_15 = csvread('H2O_15K.csv',1,0);
etc.....
So I want to make a cell at the beginning of my code looking like this and then a for loop that just reads them automatically.
input = {'co_15' 5;'co_25' 5;...
'co2_15' 5; 'co2_80' 5;...
'h2o_15' 1; 'h2o_140' 1;...
'methanol_15' 5;'methanol_120' 5;'methanol_140' 5;...
'ethanol_15' 5;'ethanol_80' 1;'ethanol_140' 5;...
'co2_ethanol_15' 5 ;'co2_ethanol_80' 5;...
'h2o_ethanol_15' 1 ;'h2o_ethanol_140' 1;...
'methanol_ethanol_15' 5;'methanol_ethanol_120' 5;'methanol_ethanol_140' 5};
for n = 1:size(input,1)
input{n,1} = csvread(strcat(input{n,1},'k.csv'),input{n,2},0);
end
The cell in this code is 19 rows and 2 columns, the rows are all the files and the columns will contain the parameters to handle the data. Now the problem I can't find a solution for is that my first column is a string name and I want that string name to be the name of the variable where csvread writes its data to but the way I set it up now it just overwrites the string in the first column of the cell with the csv data. To be extra clear I want my matlab workspace to have variables with string names in the first column containing the data of my csv files. How do I solve this?
You don't actually want to do this. Even the Mathworks will tell you not to do this. If you are trying to use variable names to keep track of related data like this, there is always a better data structure to hold your data.
One way would be to have a cell array
data = cell(size(input(:,1)));
for n = 1:size(input,1)
data{n} = csvread(strcat(input{n,1},'k.csv'),input{n,2},0);
end
Another good option is to use a struct. You could have a single struct with dynamic field names that correspond to your data.
data = struct();
for n = 1:size(input,1)
data.(input{n,1}) = csvread(strcat(input{n,1},'k.csv'),input{n,2},0);
end
Or actually create an array of structs and hold both the name and the data within the struct.
for n = 1:size(input, 1)
data(n).name = input{n,1};
data(n).data = csvread(strcat(input{n,1},'k.csv'),input{n,2},0);
end
If you absolutly insist on doing this (again, it's is very much not recommended), then you could do it using eval:
for n = 1:size(input, 1)
data = csvread(strcat(input{n,1},'k.csv'),input{n,2},0);
eval([input{n, 1}, '= data;']);
end
I have a loop which runs 100 times. In each iteration there is a string, double and a table assigned, and in the next iteration new values are assigned for them. What I want to do is to accumulate these values and after the loop finishes save the total result as result.mat using the matlab save function. I've tried putting them in cell-array but its not working so far, so if anyone could please advise how this can be done.
This is what I did:
results_cell=(100,3);
.
.
.
results_cell(i,1)=stringA;
results_cell(i,2)=TableA;
results_cell(i,3)=DoubleA;
But it gives this error Coversion to Cell from Table is not possible. So I've tried converting TableA to array of Doubles using table2array but I still get this Coversion to Cell from Double is not possible
I think using a structure would be a good way to store your data, since they are of different types and you can assign it meaningful field names for easy reference.
For example, let's call the structure Results. You can initialize it like so.
Results = struct('StringData',[],'TableData',[],'DoubleData',[])
Since you know its dimensions, you can even do this:
N = 100;
Results(N).StringData = [];
Results(N).TableData = [];
Results(N).DoubleData = [];
This automatically create a 1xN structure with 3 fields.
Then in your loop you can assign each field with its associated data like so:
for k = 1:N
Results(k).StringData = String(k);
Results(k).TableData = Table(k);
Results(k).DoubleData = Double(k);
end
where String(k), Table(k) and Double(k) are just generic names for your actual data.
When you're done with the loop you can access any type of data using a single index and the right field name.
In order to save a .mat file, use something like this:
save SomeFileName.mat Results
Which you can load into the workspace as you would with any .mat file:
Eg:
S = load('SomeFileName.mat')
R = S.Results
Hope that helps!
I have a matlab structure that follows the following pattern:
S.field1.data1
...
.field1.dataN
...
.fieldM.data1
...
.fieldM.dataN
I would like to assign values to one data field (say, data3) from all fields simultaneously. That would be semantically similar to:
S.*.data3 = value
Where the wildcard "*" represents all fields (field1,...,fieldM) in the structure. Is this something that can be done without a loop in matlab?
Since field1 .. fieldM are structure arrays with identical fields, why not make a struct array for "field"? Then you can easily set all "data" members to a specific value using deal.
field(1).data1 = 1;
field(1).data2 = 2;
field(2).data1 = 3;
field(2).data2 = 4;
[field.data1] = deal(5);
disp([field.data1]);
A loop-based solution can be flexible and easily readable:
names = strtrim(cellstr( num2str((1:5)','field%d') )); %'# field1,field2,...
values = num2cell(1:5); %# any values you want
S = struct();
for i=1:numel(names)
S.(names{i}).data3 = values{i};
end
In simple cases, you could do that by converting your struct into a cell array using struct2cell(). As you have a nested structure, I don't think that will work here.
On the other side, is there any reason why your data is structured like this. Your description gives the impression that a simple MxN array or cell array would be more suitable.