bltk_plot: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/bltk_plot - from package: bltk
/usr/lib64/bltk/bin/bltk_plot - from package: bltk

You may install the required package with command yum install {package}

Error in other languages:
bltk_plot: bevel nie gevind nie
bltk_plot: comandă negăsită
bltk_plot: comando não encontrado
bltk_plot: commande introuvable
bltk_plot: command not found
bltk_plot: käsku ei ole
bltk_plot: không tìm thấy lệnh
bltk_plot: komanda nerasta
bltk_plot: Kommando nicht gefunden.
bltk_plot: kommandot finns inte
bltk_plot: komut yok
bltk_plot: nie znaleziono polecenia
bltk_plot: níor aimsíodh an t-ordú
bltk_plot: no se encontró la orden
bltk_plot: no s'ha trobat l'ordre
bltk_plot: opdracht niet gevonden
bltk_plot: parancs nem található
bltk_plot: perintah tidak ditemukan
bltk_plot: príkaz nenájdený
bltk_plot: příkaz nenalezen
bltk_plot: команда не найдена
bltk_plot: командата не е открита
bltk_plot: 命令找不到
bltk_plot: コマンドが見つかりません