Bin data and fit curve

Hi, I have the following data:

- A vector of physical stimulus properties, something like: [0.8, 0.7, 0.56,0.4,....,0.01]

- For each of the vector's elements, the response of the subject (either "0" or "1").

What I want: I want to bin the data with the physical stimuli, and determine the percentage of "1"s responded for this bin (it would be the percentage of correct answers for the bin).

Additionally, I want a curve fittet through these percentages. I know about the hist function, but I am not sure of how I can apply it here. Thanks

[Farooq Muhammad]

hi all

i want the answer to simulation question.

i have the error plot of height above the sea level w.r.t to some reference system.

i want to bin the x axis and curve fit the bins using curve fitting tool or something else to know how error is behaving w.r.t height above the sea level.

help requierd.

Answer 1

[Walter Roberson]

binedges = 0 : 0.1 : 1;            %set as appropriate

[~, ~, binnumber] = histcounts( StimulusVector, binedges );
maxbin = max(binnumber);
count0 = accumarray(binnumber, Response == '0', [1 maxbin]);
count1 = accumarray(binnumber, Response == '1', [1 maxbin]);
total_for_bins = count0 + count1;
percent_per_bin = count1 ./ max(1,total_for_bins) * 100;

If you only need the percentages and not the counts, you can make this a bit shorter:

binedges = 0 : 0.1 : 1;            %set as appropriate

[~, ~, binnumber] = histcounts( StimulusVector, binedges );
percent_per_bin = accumarray(binnumber, Response == '1', [], @mean) * 100;

To fit a curve:

x = (binedges(1:end-1) + binedges(2:end))/2;
y = percent_per_bin;

and now you can fit your curve on x and y using whatever distribution seems suitable. You might want to look inside histfit() to see how it does the fitting and plotting.

[MiauMiau]

Thanks! But I get the following error for my implementation:

% my variables
  ThumbArray=[0.07,0.0805,0.068425,0.05816125,0.0494370625,0.042,0.0357182776562500,0.0303605360078125,0.0258064556066406,0.0219354872656445];
  responseThumb=[3,1,1,1,1,1,1,1,1,1];

    binedges = 0 : 0.01 : max(ThumbArray);   %set as appropriate
    [~, ~, binnumber] = histcounts( ThumbArray, binedges );

    percent_per_bin = accumarray(binnumber, responseThumb == '1', [], @mean) * 100;

    %Curve fitting:

    x = (binedges(1:end-1) + binedges(2:end))/2;
    y = percent_per_bin;

Error:

Error using accumarray
Second input VAL must be a vector with one element for each row in SUBS, or
a scalar.

Error in fitStaircase (line 14)
percent_per_bin = accumarray(binnumber, responseThumb == '1', [], @mean) *
100;

What does that mean..?

[Walter Roberson]

      percent_per_bin = accumarray(binnumber, responseThumb(:) == '1', [], @mean) * 100;

[MiauMiau]

Hm, this gives me the exact same error unfortunately

[Walter Roberson]

You could try

      percent_per_bin = accumarray(binnumber(:), responseThumb(:) == '1', [], @mean) * 100;

[MiauMiau]

thank you. I changed the maximum of binedges:

responseThumb = response(finger==1);

binedges = 0 : 0.01 : max(ThumbArray)+0.01;            %set as appropriate
[~, ~, binnumber] = histcounts( ThumbArray, binedges );

percent_per_bin = accumarray(binnumber(:), responseThumb(:) == '1', [], @mean) * 100;
%To fit a curve:

x = (binedges(1:end-1) + binedges(2:end))/2;
y = percent_per_bin;

And it is not throwing an error - however, y is a zero-vector. Why is that?

[Walter Roberson]

You wrote that the response is (either "0" or "1") so my interpretation is that the responses are the characters '0' or '1' . If they are instead the numeric values 0 or 1 then change the '1' in the code to plain 1

[MiauMiau]

thx!