Want to read take the values in an excel file and calculate the equation

I am creating a code that reads an Excel file's values line by line then calculates the spectral line intensity equation using the values of each line of the Excel sheet. After taking the calculation, it moves on to the next line and does the same thing in a loop. I am trying to figure out how to tell Excel to read one line at a time, use the values of that line to calculate the equation, and then move on to the next and then store that calculation. This is what I have so far:

clear all
sdata = readtable('3057-3058.xlsx', 'Range', 'B1:K34')

Warning: Column headers from the file were modified to make them valid MATLAB identifiers before creating variable names for the table. The original column headers are saved in the VariableDescriptions property.
Set 'VariableNamingRule' to 'preserve' to use the original column headers as table variable names.

sdata = 33×10 table
      v           S            A        yair     yself      E_      nair    x_air     J_    J__1
    ______    _________    _________    _____    _____    ______    ____    ______    __    ____

    3057.2    2.892e-25      0.05955    0.045    0.059    1780.1     0.6     -0.01    19     18 
    3057.2    2.237e-25      0.04603    0.045    0.059      1780     0.6     -0.01    19     18 
    3057.2    7.842e-26    0.0003846    0.047    0.065     950.3    0.62     -0.01    14     13 
    3057.2    1.331e-27    5.231e-05    0.046    0.061    1417.1    0.61     -0.01    17     16 
    3057.3    6.537e-25       0.2403    0.044    0.069      1639    0.75    -0.006     5      4 
    3057.3    1.052e-24      0.09416    0.047    0.094    1487.8    0.75    -0.006     6      5 
    3057.4    1.974e-23       0.1451    0.039    0.065    950.13    0.62     -0.01    14     13 
    3057.4    3.328e-29    0.0001196    0.045    0.057    2397.8    0.58     -0.01    22     21 
    3057.4    2.958e-23        0.145    0.047    0.065    950.14    0.62     -0.01    14     13 
    3057.5    1.225e-26    0.0001137    0.047    0.065    1095.3    0.62     -0.01    15     14 
    3057.5    5.301e-25       0.2012    0.032    0.055    1674.5    0.75    -0.006     9      8 
    3057.5    4.503e-23       0.1324    0.048    0.065    950.15    0.62     -0.01    14     13 
    3057.5    2.395e-25      0.03688    0.044    0.068    1459.9    0.75    -0.006     5      5 
    3057.5    6.816e-25       0.1724    0.044    0.069    1674.4    0.75    -0.006     9      8 
    3057.6    1.379e-24        0.198    0.047    0.099    1640.2    0.75    -0.006     8      8 
    3057.6    7.132e-26      0.09447    0.046    0.058    2183.1    0.59     -0.01    21     20 

Ia = 9.88274*10^-1;
p = pi;
c = 2.998*10^10;
g1 = 1;
c2 = 1.4387769;
T = 296;
Q = 5.9053*10^2;
for k = 1:length(sdata)
    S = (Ia)*(A / (8*(p)*(c)*(v)^2))*(((g1)*exp(1))*(1 - (exp(1))/(Q)));
end

Error using tabular/length
Undefined function 'LENGTH' for input arguments of type 'table'. Use the height, width, or size functions instead.

[Dyuman Joshi]

Use size() instead of length as the error (clearly) suggests.

You have written a loop but there is no loop index in the for loop code? And it is just overwriting the variable S.

Answer 1

[Pulkit]

As per my understanding, you want to read data from an EXCEL file, perform some calculation and then write output data back to the EXCEL file. Here you are using values of variable A and v from the Excel sheet. All other variables have constant values.

• I also see that you have used ‘readtable’ function. Please refer the following documentation link to know more about accessing variables from table

Create table from file - MATLAB readtable (mathworks.com)

• Also ‘length’ function is not defined for table type instead use ‘size’ function. Please refer to the following documentation link

Array size - MATLAB size (mathworks.com)

Here you can achieve this as follows:

clear all;
sdata = readtable('3057-3058.xlsx', 'Range', 'B1:K34','VariableNamingRule','preserve');
Ia = 9.88274*10^-1;
p = pi;
c = 2.998*10^10;
g1 = 1;
c2 = 1.4387769;
T = 296;
Q = 5.9053*10^2;
v=sdata.v;  % storing value of v from sdata table
A=sdata.A;  % storing value of A from sdata table

% with for loop as you mentioned
for k = 1:size(sdata)
    S(k,1) = (Ia)*(A(k) / (8*(p)*(c)*(v(k))^2))*(((g1)*exp(1))*(1 - (exp(1))/(Q)));
end
 
% you may also achieve this in vector form without use of loop(method2)
S_new=(Ia)*(A(:) ./ (8*(p)*(c)*(v(:)).^2))*(((g1)*exp(1))*(1 - (exp(1))/(Q)));

Refer the following documentation for Right array division and element wise power operation

Element-wise power - MATLAB power .^ (mathworks.com)

Right array division - MATLAB rdivide ./ (mathworks.com)

Please refer the following documentation for writing data to excel sheet.

Write table to file - MATLAB writetable (mathworks.com)

Hope this answers your question.