MATLAB: How can i write a line from an excel file to a matrix

beginner questionsmatrixxlsread

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It's ok i found a way to do it!! (it was quite simple actually but i am totally new in programming)!

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MATLAB: How to read only specific columns in from an Excel file, not consecutive columns

I enclose a first version of a function I just wrote. This will read a number of columns from a large Excel file. Since it opens the Excel file only once, it is significantly faster than repeated calls to xlsread, reading one column at a time.

No error checks so far. A crash may leave an Excel process running. End it using the Windows tast manager

 function data = read_excel_columns(filename,sheet,columns,firstrow,lastrow)
% Read selected columns from large Excel sheet using ActiveXServer
%  filename:  Seems that you have to use the full path to the Excel file
%  sheet   :  e.g. 'Sheet1'
%  columns :  array of column mumbers, e.g [17,341,784]
%  firstrow, lastrow:  The first and last rows to be read 
%  data:   : array of numerical values
%
% Are Mjaavatten, 2016-03-14
    nrows = lastrow-firstrow+1;
    ncols = length(columns);
    data = zeros(nrows,ncols);
    first = num2str(firstrow);
    last = num2str(lastrow);
    hExcel = actxserver('Excel.Application');
    hWorkbook = hExcel.Workbooks.Open(filename);
    hWorksheet = hWorkbook.Sheets.Item(sheet);
    for i = 1:ncols
        col = col2str(columns(i));
        Range = [col,first,':',col,last];
        RangeObj = hWorksheet.Range(Range);
        data(:,i) = cell2mat(RangeObj.value);
    end
    release(hWorksheet)
    release(hWorkbook)
    release(hExcel)
end
 function colname = col2str(n)
% Translate Excel column number to Column characters 
    s = '';
    while n > 0
        s = [s,char(mod(n-1,26)+65)];
        n = floor((n-1)/26);
    end
    colname = deblank(fliplr(s));
end

MATLAB: How to plot a piecewise function

Solution usin if statement:

x=linspace(-5,30,1000);
for i=1:1000
if x(i)<0
     y(i)=10;
elseif x(i)>=0 & x(i)<9
y(i)=10*x(i)+10;
   else 
y(i)=15*sqrt(4*x(i))+10;
end
end
plot(x,y)

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MATLAB: How to read only specific columns in from an Excel file, not consecutive columns

MATLAB: How to plot a piecewise function

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