How do I specify the error values for a bar plot?

Error values can be specified in several ways. You can directly enter the error values as a vector using the `yerr` or `xerr` property of the `errorbar` function. You can also calculate the error values based on the data using functions like `sqrt(sum((x_values - mean(x_values))^2))` for standard deviation or `std(y_values)` for standard deviation. Alternatively, you can use the `errorbar` function's `propagation` property to control the error bar's behavior.