How to get specific points for certain value from multiple excel files and insert them into the figure as legend?

Hello,

i have two questions that are somewhat related.

1) i have mutliple excel files that contains columns of data;

example (inserting in the code, as not sure how to put the table in);

i want to find the row of time, p1, p2 & s for a value of v that is close to certain number, example 35.4.

i want to find row of those data for each file.

2) the 2nd question is, i have a figure with plot of time, P2 for all the files (1 figure containing multiple plots)

how do i tell MATLAB to insert the values from question 1 for corresponding plots in the figure as legend.

Time 	P1	    P2	            V	        S
0.01	100	    14.14214	29.02181	5.38719
0.02	110	    14.8324	    30.55477	5.527637
0.03	120	    15.49193	32.01912	5.658544
0.04	130	    16.12452	33.42332	5.781291
0.05	140	    16.7332	    34.77423	5.896968
0.06	150	    17.32051	36.0775	    6.006455
0.07	160	    17.88854	37.33783	6.110469
0.08	170	    18.43909	38.55921	6.209606
0.09	180	    18.97367	39.74504	6.304367
0.1	    190	    19.49359	40.89826	6.395175

Answer 1

[dpb]

With the added information, I'd do something more like

Vtarget=35.4;
[files, path] = uigetfile ('.xlsx', 'MultiSelect', 'on');
if ischar(files), files=cellstr(files); end     % handle one file is char string, not cell array
nFiles=numel(files);
hL=gobjects(nFiles,1);                          % preallocate graphics handles array
for i = 1:nFiles
  fullfilename=fullfile(path,files(i));         % use fullfile to build; returns cellstr
  tdata=readtable(fullfilename{:});             % and read the spreadsheet to table
  ix=interp1(tdata.V,1:height(tdata),Vtarget,'nearest');    % find the nearest point for V
  lgd=compose('Vtarget =%f.1',tdata.V(ix));     % build the display string for legend nearest V value
  hL(i)=plot(tdata.Time, tdata.P2,'DisplayName',lgd);  % plot the P2 variable; don't duplicate same data
  if i==1, hold on, end                         % prepare add more to same figure
end
legend

[Gopal New]

Thanks

Answer 2

[dpb]

t=array2table(data,'VariableNames',{'Time','P1','P2','V','S'});
Vtarget=35.4;
ix=interp1(t.V,1:height(t),35.4,'nearest')
ix =
     5
>> t(ix,:)
ans =
  1×5 table
    Time    P1       P2        V         S  
    ____    ___    ______    ______    _____
    0.05    140    16.733    34.774    5.897
>> 

To write a legend, use compose or num2str

legend(compose('Value for Vtarget =%d',Vtarget)

Salt to suit...

[Gopal New]

i'm getting error with 'array2table.'

'Error using table (line 281)

Invalid parameter name: O.

Error in array2table (line 58)

t = table(vars{:});'

Caused by:

You may have intended to create a table with one row from one or more variables that are character strings. Consider using

cell arrays of strings rather than character arrays. Alternatively, create a cell array with one row, and convert that to a

table using CELL2TABLE.'

not sure if it has to do with the fact that i'm using excel files.

Some background: i'm using uigetfile to load multiple files and using a for loop to plot.

[dpb]

" i'm using uigetfile to load multiple files..."

uigetfile doesn't "load" anything -- all it does is return an array of filenames.

[Gopal New]

obiviously using 'xlsread' to read the data and plot. what i'm saying is that i can't seem to use what you proivded with the script to get the result i'm looking for.

[dpb]

"obiviously using 'xlsread' ..."

How is that "obvious"??? We can't see your terminal from here and you've posted zero lines of code.

xlsread is deprecated and not recommended; use readtable if you want a table.

The code I provided presumed your data were in an array; if not yet there, then you'll need to use whatever form you do have.

It's really not possible to provide specific answers without knowing what it is are dealing with which means we need to see the code itself (and an example of the spreadsheet never hurts).

[dpb]

doc readtable
...
See Also
...
Introduced in R2013b

readtable was introduced in R2013b so it should work just fine with R2016.

[Gopal New]

when using 'readtable', th e following error occurs

"Error using plot

Non-numeric data is not supported in 'Line'

Error in Test_2 (line 18)

plot (Time, P2)"

This doesn't happen with 'xlsread.'