MATLAB: Graphing Base Form of y=mx+b from a .csv file

csvdataMATLABslope-intercepttrendline

I have a few thousand equations in y=mx+b form that I have acquired from hundreds of thousands of data points in multiple excel files. They are all trendlines of similar T-s data. I am attempting to create generalized trendlines of similar data types and I would like to be able to select formulas in y=mx+b form that I would like plotted, and then find the formula for the LOBF (Line of best fit) for that set of equations. I am new to MatLab and would just like some assistance in this.

Best Answer

I'm assuming you've read the data into Matlab and you've got a cell array of strings or character arrays named "data" that appears like this:
data =
  3×6 cell array
  Columns 1 through 3
    {'y = 2.3297x + 1…'}    {'y = 1.8866x + 1…'}    {'y = 0.3373x + 1…'}
    {'y = 1.9526x + 9…'}    {'y = 1.7754x + 9…'}    {'y = 2.774x + 68…'}
    {'y = 1.9004x + 9…'}    {'y = 1.9833x + 8…'}    {'y = 3.1304x + 6…'}
  Columns 4 through 6
    {'y = 3.584x + 69…'}    {'y = 2.1044x + 6…'}    {'y = 0.0704x + 6…'}
    {'y = 3.0042x + 6…'}    {'y = 2.3015x + 5…'}    {'y = 0.1415x + 6…'}
    {'y = 3.1099x + 6…'}    {'y = 2.466x + 60…'}    {'y = 0.2486x + 6…'}
Execute these two lines below to extract the slope and intercept values from each string. 
numVals = regexp(data,'[+-]?\d+\.?\d*', 'match');
mb = cellfun(@str2double, numVals, 'UniformOutput', false);
mb is a cell array the same size as "data" and contains the [slope,intercept] of each cell element. 
mb =
  3×6 cell array
    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}
    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}
    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}    {1×2 double}
For example, for the equation in data(2,3), the slope and intercept are
   mb{2,3}
ans =
        2.774       68.856
To draw a regression line on a plot use refline()
 refline(mb{2,3})
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