I have imported a matrix X filled with data, and its according headers for each column into MATLAB. Now the problem is how can I rename each column of X by its according name in the header cell.I would like to do this in a loop.
Would anyone tell me how can I loop a rename programme in this situation?
I suggest creating a structure out of the data, rather than individual variables. Even with a large number of columns, this will not clutter the workspace, nor will it overwrite variables already in the workspace in the case of a name collision. It will keep all the data from the spreadsheet together, and still allowing access to it by column name. To easily create a structure from a cell array of column names and a matrix of data, use cell2struct:
>> colnames = {'odds','evens'};
>> data = [1 2;3 4;5 6];
>> spreadsheet_structure = cell2struct(num2cell(data,1), colnames, 2)
spreadsheet_structure =
odds: [3x1 double]
evens: [3x1 double]
(num2cell(M,1) creates a cell array in which each cell is a column from matrix M)
Loop through the header columns and use eval to create variables with names contained as strings in your matrix "header":
[X,header,~] = xlsread('eaef21.xls',1,'A1:AY541');
for H = 1:size(header,2)
eval([header(1,H), " = X(:,", H, ");"]);
end
Also it is often very useful to replace the eval above with disp until you are satisfied that it is working as you want it to. Using disp will help you understand what is going on as well.
Related
so I am trying to read multiple sheets in excel using matlab by this function:
Data_mat=readmatrix('DATA_I.xlsx');
I tried a couple of things using additional info, bu seems not correct.
If you want the output to be a matrix, use that command. On the other hand, if you want to read tables (considering the column name), you can use the readtable command.
I generated a dummy excel file that only contains 2 sheets with some numbers there. If you want to read the matrices, use the readmatrix, or if you want tables, just change that function to readtable. Both functions have the same argument structure.
% Define the file name
FileName = "MatrixesInFile.xlsx";
% Get the sheets in the excel file
Sheets = sheetnames(FileName);
% Generate the variable with the matrices
myMatrices = struct;
% Read the matrices and store it in the struct
for n=1:length(Sheets)
% Get evaluated sheet
eval_sheet = Sheets{n};
% Get the matrix
values = readmatrix(FileName,'Sheet',eval_sheet);
% Create a field in the struct and store the matrix there
myMatrices.(eval_sheet) = values;
end
% Print the variable
myMatrices
I am trying to get some variables and numbers out from an Excel table using Matlab.
The variables below named "diffZ_trial1-4" should be calculated by the difference between two columns (between "start" and "finish"). However I get the error:
Undefined operator '-' for input arguments of type"
'cell'.
And I have read somewhere that it could be related to the fact that I get {} output instead of [] and maybe I need to use cell2mat or convert the output somehow. But I must have done that wrongly, as it did not work!
Question: How can I calculate the difference between two columns below?
clear all, close all
[num,txt,raw] = xlsread('test.xlsx');
start = find(strcmp(raw,'HNO'));
finish = find(strcmp(raw,'End Trial: '));
%%% TIMELINE EACH TRIAL
time_trial1 = raw(start(1):finish(1),8);
time_trial2 = raw(start(2):finish(2),8);
time_trial3 = raw(start(3):finish(3),8);
time_trial4 = raw(start(4):finish(4),8);
%%%MOVEMENT EACH TRIAL
diffZ_trial1 = raw(start(1):finish(1),17)-raw(start(1):finish(1),11);
diffZ_trial2 = raw(start(2):finish(2),17)-raw(start(2):finish(2),11);
diffZ_trial3 = raw(start(3):finish(3),17)-raw(start(3):finish(3),11);
diffZ_trial4 = raw(start(4):finish(4),17)-raw(start(4):finish(4),11);
You are right, raw contains data of all types, including text (http://uk.mathworks.com/help/matlab/ref/xlsread.html#outputarg_raw). You should use num, which is a numeric matrix.
Alternatively, if you have an updated version of Matlab, you can try readtable (https://uk.mathworks.com/help/matlab/ref/readtable.html), which I think is more flexible. It creates a table from an excel file, containing both text and numbers.
In my code I'm trying to use load with entries from a cell, but it is not working. The portion of my code below produces a 3 dimensional array of strings. The strings represent the paths to file names.
for i = 1:Something
for j = 1:Something Different
for k = 1: Yet Something Something Different
DataPath{j,k,i} = 'F:\blah\blah\blah\fileijk %file changes based on i,j,and k
end
end
end
In the next part of the code I want to use load to open the files using the path names defined in the code above. I do this using the code below.
Dummy = DataPath{l,(k-1)*TSRRange+m};
Data = load(Dummy);
The idea is for Dummy to take the string content out of DataPath so I can use it in load. By doing this I thought that Dummy would be defined as a string and not a cell, but this is not the case. How do I pull the string out of DataPath so I can use it with load? Thanks.
I have to load the data this way because the data is located in multiple folders. I can post more of the code if needed, but it is complex.
Dummy is a cell because you assigned a 3D cell array but are accessing a 2D cell with Dummy = Datapath{1,(k-1)*TSRRange+m}
I don't believe that you can expect to access all cell elements I this way. Instead, use three indices just as you did when creating it.
I have two excel functions that I am trying to convert into R:
numberShares
=IF(AND(N213="BOH",N212="BOH")=TRUE,P212,IF(AND(N213="BOH",N212="Sell")=TRUE,ROUNDDOWN(Q212/C213,0),0))
marketValue
=IF(AND(N212="BOH",N213="BOH")=TRUE,C213*P212,IF(AND(N212="Sell",N213="Sell")=TRUE,Q212,IF(AND(N212="BOH",N213="Sell")=TRUE,P212*C213,IF(AND(N212="Sell",N213="BOH")=TRUE,Q212))))
The cells that are referenced include:
c = closing price of a stock
n = position values of either "buy or hold" or "sell"
p = number of Shares
q = market value, assuming $10,000 initial equity (number of shares*closing price)
and the tops of the two output columns that i am trying to recreate look like this:
output
So far, in R I have constructed a dataframe with the necessary four columns:
data.frame
I just don't know how to write the functions that will populate the number of shares and market value columns. For loops? ifelse?
Again, thank you!!
Covert the AND()'s to infix "&"; the "=" to "=="; and the IF's to ifelse() and you are halfway there. The problem will be in converting your cell references to array or matrix references, and for that task we would have needed a better description of the data layout:
numberShares <-
ifelse( N213=="BOH" & N212=="BOH",
#Perhaps PosVal[213] == "BOH" & PosVal[212] == "BOH"
# ... and very possibly the 213 should be 213:240 and the 212 should be 212:239
P212,
ifelse( N213=="BOH" & N212=="Sell" ,
round(Q212/C213, digits=0),
0))
(You seem to be returning incommensurate values which seems preeety questionable.) Assuming this is correct code despite my misgivings the next translation involves apply the same substitutions in this structure (although you seem to be missing an else-consequent in the last IF function:
marketValue <-
IF( AND(N212="BOH", N213="BOH")=TRUE,
C213*P212,
IF(AND(N212="Sell",N213="Sell")=TRUE,
Q212,
IF( AND(N212="BOH",N213="Sell")=TRUE,
P212*C213,
IF(AND(N212="Sell",N213="BOH")=TRUE,
Q212))))
(Your testing for AND( .,.)=TRUE is I believe unnecessary in Excel and certainly unnecessary in R.)
I'm trying to use get() to access a list element in R, but am getting an error.
example.list <- list()
example.list$attribute <- c("test")
get("example.list") # Works just fine
get("example.list$attribute") # breaks
## Error in get("example.list$attribute") :
## object 'example.list$attribute' not found
Any tips? I am looping over a vector of strings which identify the list names, and this would be really useful.
Here's the incantation that you are probably looking for:
get("attribute", example.list)
# [1] "test"
Or perhaps, for your situation, this:
get("attribute", eval(as.symbol("example.list")))
# [1] "test"
# Applied to your situation, as I understand it...
example.list2 <- example.list
listNames <- c("example.list", "example.list2")
sapply(listNames, function(X) get("attribute", eval(as.symbol(X))))
# example.list example.list2
# "test" "test"
Why not simply:
example.list <- list(attribute="test")
listName <- "example.list"
get(listName)$attribute
# or, if both the list name and the element name are given as arguments:
elementName <- "attribute"
get(listName)[[elementName]]
If your strings contain more than just object names, e.g. operators like here, you can evaluate them as expressions as follows:
> string <- "example.list$attribute"
> eval(parse(text = string))
[1] "test"
If your strings are all of the type "object$attribute", you could also parse them into object/attribute, so you can still get the object, then extract the attribute with [[:
> parsed <- unlist(strsplit(string, "\\$"))
> get(parsed[1])[[parsed[2]]]
[1] "test"
flodel's answer worked for my application, so I'm gonna post what I built on it, even though this is pretty uninspired. You can access each list element with a for loop, like so:
#============== List with five elements of non-uniform length ================#
example.list=
list(letters[1:5], letters[6:10], letters[11:15], letters[16:20], letters[21:26])
#===============================================================================#
#====== for loop that names and concatenates each consecutive element ========#
derp=c(); for(i in 1:length(example.list))
{derp=append(derp,eval(parse(text=example.list[i])))}
derp #Not a particularly useful application here, but it proves the point.
I'm using code like this for a function that calls certain sets of columns from a data frame by the column names. The user enters a list with elements that each represent different sets of column names (each set is a group of items belonging to one measure), and the big data frame containing all those columns. The for loop applies each consecutive list element as the set of column names for an internal function* applied only to the currently named set of columns of the big data frame. It then populates one column per loop of a matrix with the output for the subset of the big data frame that corresponds to the names in the element of the list corresponding to that loop's number. After the for loop, the function ends by outputting that matrix it produced.
Not sure if you're looking to do something similar with your list elements, but I'm happy I picked up this trick. Thanks to everyone for the ideas!
"Second example" / tangential info regarding application in graded response model factor scoring:
Here's the function I described above, just in case anyone wants to calculate graded response model factor scores* in large batches...Each column of the output matrix corresponds to an element of the list (i.e., a latent trait with ordinal indicator items specified by column name in the list element), and the rows correspond to the rows of the data frame used as input. Each row should presumably contain mutually dependent observations, as from a given individual, to whom the factor scores in the same row of the ouput matrix belong. Also, I feel I should add that if all the items in a given list element use the exact same Likert scale rating options, the graded response model may be less appropriate for factor scoring than a rating scale model (cf. http://www.rasch.org/rmt/rmt143k.htm).
'grmscores'=function(ColumnNameList,DataFrame) {require(ltm) #(Rizopoulos,2006)
x = matrix ( NA , nrow = nrow ( DataFrame ), ncol = length ( ColumnNameList ))
for(i in 1:length(ColumnNameList)) #flodel's magic featured below!#
{x[,i]=factor.scores(grm(DataFrame[, eval(parse(text= ColumnNameList[i]))]),
resp.patterns=DataFrame[,eval(parse(text= ColumnNameList[i]))])$score.dat$z1}; x}
Reference
*Rizopoulos, D. (2006). ltm: An R package for latent variable modelling and item response theory analyses, Journal of Statistical Software, 17(5), 1-25. URL: http://www.jstatsoft.org/v17/i05/