Description Usage Arguments Details Value Author(s)
This function follows closely upon that described in Cohen's paper
1 2 3  cat_lines1(params, fit_it = TRUE, data, start_pts, k_bounds, o_bounds,
s_bounds, den_sd_cutoff, den_ratio_cutoff, num_checkFirst = 5,
num_checkLast = 10)

params 
A vector of parameters for optimization, the three values in it refer to slope, offset, and sd 
fit_it 
A bollean variable; if it is TRUE, the function will return fit measure; if it is FALSE, the function will return fit information 
data 
A data.frame storing the fixation data including at least the x_pos and y_pos of each fixation 
start_pts 
A data.frame containing the starting position of each text line. It has three columns:

k_bounds 
A list containing the lower and upper boundaries of slope; default value is [0.1, 0.1] 
o_bounds 
A list containing the lower and upper boundaries of offset; defaul value is [0.5*dist of adjacent text lines, 0.5*dist of adjacent text line]) 
s_bounds 
A list containing the lower and upper boundaries of sd; default value is [1, 20] 
den_sd_cutoff 
A float variable for cutoff threshold for density; If it is Inf, use mean(inv_dnorm(exp(data_den_max))) + 3*sd(inv_dnorm(exp(data_den_max))) as cutoff (99.7% are accepted) 
den_ratio_cutoff 
A float variable for cutoff threshold for density ratio (ratio between the maximum density and second maximum density) 
num_checkFirst 
An integer denoting the number of starting fixations used for checking startreading bound; default value is 5 
num_checkLast 
An integer denoting the number of ending fixations used for checking endreading bound; default value is 10 
This function optimizes the slope, offset and sd for all lines of fixations. It uses sum(data_den_max) as fit measure for optimization.
A data.frame including fixation data, and fitting data including fit measures and fitted lines information. It adds the following columns:
line: Text line that each fixation belongs to
y_line: y position of the text line that each fixation is assigned to
y_res: Residualized y position of each fixation y_line + y_res will give the original y position of each fixation
slope: Optimized slope value for all fitted lines
offset: Optimizaed offset value for all fitted lines
sd: Optimized sd value for all fitted lines
fit_den: fitted density value
fit_y_diff: fitted y difference (accumulated y differences between each fixation and the fitted line)
Tao Gong [email protected]
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