You don't show us your code, but I am guessing you neglected to add a column of ones to your x input, as described in the documentation:
This code will give you the two-parameter output you expect:
x = [ones(3,1),rand(3,1)]; y = rand(3,1); b = regress(y,x)
I don't have regress(). Please list what Product (toolbox) is is in below your question in the Product box.
You can use polyfit() which is in base MATLAB to get the slope and intercept in one line. Here's a full blown demo:
clc; % Create training data: x = [1 4 5 6] y = [4 6 7 9]
% Do the regression. coefficients = polyfit(x, y, 1); % 1 means a line slope = coefficients(1) intercept = coefficients(2) % We're done!
% Plot training data: plot(x, y, 'bo', 'LineWidth', 3); hold on;
% Plot fit numberOfPoints = 100; fitX = linspace(min(x), max(x), numberOfPoints); fitY = polyval(coefficients, fitX); plot(fitX, fitY, 'r-', 'LineWidth', 3); grid on; xlabel('X', 'FontSize', 30); ylabel('Y', 'FontSize', 30);